What happens when DNA testing cannot identify a child’s father?

The recent Court of Appeal decision in Re P has clarified an important but difficult question in family law: when does being named as a child’s father create parental responsibility? In the unusual circumstances of Re P, where DNA testing could not distinguish between two identical twin brothers, the case highlights the limits of genetic evidence, the importance of legal parentage, and the profound impact that uncertainty over paternity can have on a child’s identity and future.

The case of Re P

The case of Re P [2026] EWCA Civ 344 dealt with a truly unusual situation: a child’s father couldn’t be identified, even with DNA testing. The child’s mother had relationships with both of a pair of identical twins within a week of the likely conception date. Because identical twins share the same DNA, the tests couldn’t show which twin was the biological father.

This situation created real problems. It made it impossible to know who should be listed as the father on the birth certificate, who should have legal rights and responsibilities for the child, and what the child’s future would look like.

Sir Andrew McFarlane, President of the Family Division 2018–2026, explained that under the law, a father is usually someone who is proven to be the child’s genetic parent. But here, while it was certain that one of the twins was the father, the science couldn’t pinpoint which one. One twin had been listed as the father on the birth certificate, but because both had a 50% chance of being the father, the court decided to remove his name. This meant that neither twin had parental responsibility for the child.

The Court also pointed out that not knowing who their biological father is can have a big effect on a child’s sense of identity and emotional wellbeing. The judge encouraged the mother to think about how she would explain the situation to her child as she grew up. It was noted that the possibility of future advances in science may make it possible to identify the father.

What is parental responsibility?

Parental responsibility includes the rights, duties, powers, and authority a parent has regarding their child and the child’s property – for example, decisions over schooling, religion, medical treatment, and where the child lives. Usually, this lasts until the child turns 18.

In this case, neither potential father will have the right to make any decision regarding the child despite the fact one of them is the 100% biological father.

Why is this case important?

This case could impact future situations where paternity isn’t clear. It shows that being named on a birth certificate isn’t enough to be considered the legal father and have parental responsibility, restricting ‘fatherhood’ to a biological percentage. If another rare case arises where two identical men could be the father and DNA can’t decide, neither will be presumed to have legal rights unless the court makes a special decision based on the child’s welfare.

If you have questions or concerns about parental rights, please contact Corinne Parke, Bethan Hill-Howells, or Maisie Johnson.