23 March 2026
On 20 March 2026 The Court of Appeal published its ruling on three separate appeals concerning the status of ‘father’ and attribution of parental responsibility in Re J, M-S-K-B & P [2026] EWCA Civ 344. In all three cases, the Court was tasked with determining the legal status of the men who had been registered as ‘father’ on the child’s birth certificate and shared parental responsibility with the mother in circumstances where this was subsequently contested. In one case, it had been genuinely assumed that the man was the child’s biological father. In the second case it had always been known he was not the child’s genetic father and in practice both men had acted as a psychological or social father. In the third case, the mother had had sex with two male identical twins over the course of one week at the time conception took place and DNA testing could not distinguish which of the twins was the child’s biological father.
Fundamental Legal Issues
The cases raised a series of fundamental legal issues:
(i) Is the definition of ‘father’ for the purposes of the Children Act 1989 (“CA 1989”) limited to a child’s biological/genetic father, or does it extend to those who have acted as the child’s psychological/social father?
(ii) Where an individual is registered as a child’s ‘father’ on their birth register entry, does parental responsibility attributed by birth registration attach to a ‘father’ who is not the child’s biological/genetic father?
(iii) If, in response, to (ii), parental responsibility is conferred upon a non-biological father, is it automatically terminated upon the making of a declaration that the individual is not the child’s father under Family Law Act 1986, s55A (“FLA 1986”), or does parental responsibility continue until it is terminated by a separate court order?
(iv) If, in response to (iii), a separate court order is required to terminate parental responsibility, is this a decision determined by affording paramount consideration to the child’s welfare, or some other basis?
Additionally, in the third case, there was an added layer of complexity associated with DNA testing. DNA testing was able to establish that the child’s biological father was one of the identical twins but it could not identify which twin was the father. The DNA evidence determined that each twin had a 50 percent chance of being the genetic father, but neither was proven to be so on the balance of probabilities. Whilst one twin had been registered as ‘father’ on the child’s birth register it could not be proved or disproved that he was the father.
By the time the cases came before the Court of Appeal, all parties had abandoned arguments that the definition of ‘father’ in the CA 1989 was not limited to the child’s biological/genetic father. As such, they all came to accept that the common law definition of ‘father’ applied so that only the person whose sperm fertilised the egg and created the embryo resulting in the birth of the child could be regarded as the child’s ‘father’ (“the genetic father”). The live issues at appeal therefore focused on the legal consequences where a person who is not legally a child’s father is nevertheless registered as father on the child’s birth certificate.
Definition of ‘Father’ In Common Law
The Court of Appeal ruling stated that the Courts have consistently applied the legal principle that a child’s legal parents are the gestational mother and the genetic/biological father and that this principle is “well settled”. The Law Commission’s Report of 1982 into ‘Illegitimacy’ stated that an illegitimate child’s father is the ‘natural father’. For the first time in the Family Law Reform Act 1987, statute codified that the father of a child born outside of marriage was the child’s father as a matter of law. It also codified an evidential presumption that where a child is born within a marriage, the mother’s husband is the child’s father unless the contrary is proved. It further provided that where it is proven that another person is the father, then for common law purposes he is regarded as the child’s legal father.
Definition of ‘Father’ In The Children Act 1989
The Court of Appeal held that the definition of ‘father’ in the CA 1989 is that construed under common law.
Acquisition of Parental Responsibility
The CA 1989 introduced the concept of parental responsibility (legal decision making responsibilities for a child). It also made provision for the attribution of parental responsibility to the child’s mother, father and to those who obtain parenthood through assisted reproduction under the Human Fertilisation and Embryology Act 2008.
In respect of the acquisition of parental responsibility by an unmarried father for a child, the Court of Appeal found that in the first two cases, as the men were not genetic/biological fathers they were not a ‘father’ (in accordance with common law) under s4 CA 1989 and so never obtained parental responsibility in the first place.
Background: Re J
AJ (man registered as child’s father) and MJ (mother) had been in a relationship for some months when she became pregnant and gave birth in 2020 to J (the child) . AJ believed he was J’s father and registered the birth with MJ, recording that he was father on the birth register. Two years later their relationship ended and MJ told AJ he might not be J’s father. DNA testing was undertaken which showed that another man was J’s father. Notwithstanding this, AJ thought of himself as J’s father and wanted a continued parental relationship and in November 2023 he issued an application for a parental responsibility order. In November 2024, MJ issued an application for a Declaration of (Non) Parentage. At a High Court Hearing in December 2024, AJ conceded that a Declaration of (Non) Parentage should be made and arguments were made about what, if any, parental responsibility AJ had and should have in future.
AJ’s case was that irrespective of not being J’s father, upon registration as ‘father’ on J’s birth register he held parental responsibility pursuant to CA 1989 s4(1)(a). He asserted that when it was discovered he was not the father, this did not render his parental responsibility void ab initio (i.e. void from the start). He asserted that his parental responsibility could only be extinguished by court order and that in determining this the Court was required to give paramount consideration to the welfare of the child.
MJ’s case (mother’s case) was that as he was not J’s father, AJ never acquired parental responsibility under s4(1) CA 1989.
The Judge at first instance in the High Court ruled that as AJ was not J’s father he was not eligible to be registered as father on J’s birth register. Accordingly, he did not acquire parental responsibility on being registered as father on J’s birth register and he never held parental responsibility in practice. Accordingly, no order was required to remove parental responsibility from AJ.
Background: Re M
MM (the mother) and AM bought anonymous donor sperm over the internet. AM asserted that he had not understood that by not going through a licensed fertility clinic, he may not have legal status in relation to any child born following conception with the donor sperm. M (the child) was born in 2019 and AM was named on M’s birth register as father. MM and AM then went on to marry in 2021. Subsequent DNA testing confirmed that AM was not M’s biological father.
The local authority brought legal proceedings in the High Court for care orders for M and her three half-siblings. The local authority sought a Declaration of (Non) Parentage in respect of AM and an order terminating any parental responsibility AM may have as a result of risks that it was alleged that he posed to the children.
The Judge at first instance made a Declaration of (Non) Parentage in respect of AM on the basis that the term ‘father’ in s4 CA 1989 was limited to a child’s natural or legal father (e.g. by adoption). As a result, any parental responsibility AM held for M was lost. In the alternative, applying the welfare of the child principle, if an order removing AM’s parental responsibility was required, she would have granted this.
Background: Re P
The child (P) was the elder of two children. It was accepted that TP1 was the father of the younger child. TP1 was also named as P’s father on the birth register. However, MP (the mother) had had sex with two male identical twins over the course of one week at the time conception took place. Despite DNA testing it was not possible to establish P’s paternity other then say one of two identical twins was the father. By the time of the final hearing MP had distanced herself from TP1 and was in a closer relationship with TP2. MP and TP2 sought a declaration that TP2 was P’s father and that any parental responsibility attributed to TP1 by virtue of being registered as father should be terminated and that parental responsibility should be conferred on TP2.
In contrast, TP1 wished to retain his registration as P’s father on the birth register and asserted that he should be regarded for all legal purposes as P’s father. P’s guardian sought a declaration that either TP1 or TP2 was P’s father and that a child arrangements order should be made in TP2’s favour to confer parental responsibility upon him.
The Judge at first instance held that it was not possible to make a legal ruling in respect of P’s paternity as neither TP1 nor TP2 could prove on the balance of probabilities that they were the father. The Judge went on to acknowledge that this meant that P’s birth certificate would not be changed. The Judge then made orders whereby P spent significant time with MP, TP1 and TP2, with P’s primary base being with MP. The Judge declined to make express orders about parental responsibility in respect of TP1 and TP2 under a child arrangements order and determined that MP was free to exercise parental responsibility for P except in relation to high-level decision making (e.g. change of school or leaving the jurisdiction). The Judge also enabled TP1 and TP2 to do what was reasonable for the care of P and their sibling whilst in their care.
Court of Appeal Determination Of The Legal Issues
The Court of Appeal ruled that:
(i) The definition of ‘father’ for CA 1989 purposes is the common law definition and so limited to a child’s biological/genetic father. The definition of father does not extend to a child’s psychological/social father.
(ii) Where a person is registered as a child’s ‘father’ on their birth register, parental responsibility attributed by this registration is not conferred on that person if they are not in fact the child’s biological/genetic father. For parental responsibility to be acquired by registration on a birth certificate under s4 CA 1989 two conditions must be met:
(a) The person must be the child’s genetic/biological father; and
(b) The person must be registered as ‘father’ on the child’s birth register entry.
(iii & iv) No parental responsibility is acquired where a person is incorrectly registered as ‘father’ on a birth register entry. As a result, no question arises about whether parental responsibility is automatically terminated by the grant of a Declaration of (Non) Parentage under the FLA 1986.
Where an individual is not the child’s legal father and has not acquired parental responsibility through registration as ‘father’ on the child birth register, but is a psychological or social parent, their role can be reflected by the grant of a child arrangements order (s8 CA 1989) and attribution of parental responsibility under s12 CA 1989.
In respect of child P, the father for the purposes of the CA 1989 is limited to the common law definition of someone who is proved to be the genetic/biological father and neither TP1 or TP2 can prove this. Accordingly, TP1 was not entitled to be registered as ‘father’ on P’s birth register entry. However, TP1 was registered as P’s father on P’s register of birth entry and if he is the father then he will have acquired parental responsibility pursuant to 4(1) CA 1989. Currently, scientifically establishing which identical twin is P’s biological father cannot be achieved without very significant cost, but this may be possible to establish over time.
It is not possible to remove the ambiguity over P’s birth registration and remove TP1’s registration as P’s ‘father’ as it cannot be proved that he is not the father pursuant to section 58(1) of the FLA 1986. However, it was wrong for the court not to clarify the position by discharging any parental responsibility TP1 may have had by making an order under CA 1989 s4(2A). The basis of such discharge is that it was not proved that TP1 was P’s father and he should not have been registered as ‘father’ and so was not eligible for parental responsibility under 4(1) CA 1989. It was also not in P’s best interests for there to be continued ambiguity over TP1’s parental responsibility.
Specialist Fertility and Family Law
These cases highlight the complexity of legal issues that can arise in relation to legal parentage, birth registration, parental responsibility, DNA testing and the care and upbringing of children. Specialist fertility and family law advice and representation proactively identifies and navigates a range of legal and practical issues including:
- Complex personal and family situations.
- Conception by private sperm donation.
- Regulated sperm donation at a licensed fertility clinic.
- Assisted conception with a known sperm donor, anonymous/identity-release donor/co-parent (e.g. legal parentage, parental rights, birth registration, risks in practice and dispute mitigation etc).
- Donor conception issues/disputes (e.g. concerning formal DNA/paternity testing, direct-to-consumer genetic testing, fertility fraud, biological and legal parentage and birth certificates).
- Care and upbringing of children following a dispute with a donor/co-parent/ex-partner or parent (e.g. contact, residence, parental responsibility, specific issue or prohibited steps).
- Intra-family egg or sperm donation.
- Donor conception and issues arising from impaired fertility/infertility, cancer diagnosis/illness, unsuccessful conception attempts, gender transition, change in personal circumstances, age and later-life parenthood.
- Posthumous conception with the eggs, sperm and embryos of a deceased loved one in fertility treatment with donor conception/surrogacy (e.g. due to illness or accident).
- Legal and wider aspects of international surrogacy or a UK surrogacy arrangement and donor conception.
- Expert witness fertility, surrogacy and donor conception law services.
- Legally clarify and determine an individual’s biological parentage (e.g. seek a formal court order for DNA testing and a Declaration of Parentage).
- Legally determine and recognize an individual’s legal parenthood.
- Rectify an individual’s birth certificate (e.g. add or remove a parent’s name).
- Legally resolve a paternity dispute (i.e. following sperm donation, IVF mix-up, issues with natural conception).
- Legally resolve legal parenthood of a non-birth parent for their child following errors in completion of HFEA consent forms at UK fertility clinics.
- Resolve a dispute about paternity/legal parentage and financial provision for a child or individual.
