Twins who were separated at birth married each other without knowing they were brother and sister, a peer has claimed.

The couple were adopted as babies by different families, and neither was told that they had a twin. They met, fell in love and got married before discovering that they were blood relatives.

The British couple were granted an annulment at a special hearing at the High Court in London, Professor Lord Alton told The Times. Judges in the Family Division ruled that the marriage had never validly existed.

Lord Alton, who was told about the case by a High Court judge, said that the twins’ experience demonstrated the need to strengthen the rights of children to know the identity of their biological parents. The peer declined to name the judge or identify the case more specifically.

He argued that reforms that are currently being debated in the House of Lords threaten to undermine even existing rights.

“The right for children to know the identity of their biological parents is a human right," said Lord Alton. “There will be more cases like this if children are not given access to the truth. The needs of the child must always be paramount”.

The planned reforms, part of the Human Embryology and Tissues Bill, will also relax the rules on who is permitted to undergo fertility treatment. Clinics will not be allowed to prevent single women and same-sex couples from having the treatment. Under the Bill, doctors will instead have to ensure that patients can offer “supportive parenting”.

The Lords will vote on the Bill on Tuesday.

Annulments are usually dealt with by a county court, but the High Court can hear them if the case is particularly complex. Marriages can be annulled if the couple are closely related, if the union is bigamous, or if one of the parties was under 16 at the time of the wedding.

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