A recent large-scale Japanese study has found that couples in long-term relationships develop noticeable biological similarities. It reports that their bodies synchronize on a deep biological level, which bolsters health deep into old age for those in happy relationships, whilst exacerbating health problems for others. These findings bring into focus the importance of proactively managing our relationships, personal lives, family building and reproductive choices. Building a happy and stable relationship and family life influences not just us as individuals, but also our children and wider family and friends.