Shock for the married couple who discovered they are twins separated at birth

Mo O'Reilly, director of child placement for the British Association for Adoption and Fostering, said such an incident was traumatic but very rare.

"Thirty or 40 years ago, it would have been more likely that twins be separated and brought up without knowledge of each other."

But she claimed that there was far more openness today with adopted children about their birth parents and background.

Last year, a German brother and sister who were separated as children and fell in love after being reunited campaigned for the right to continue their relationship. Patrick Stubing was jailed for two years for incest after he had four children with Susan, who by then he knew to be his sister.

The 29-year-old locksmith was given up for adoption as a baby and did not meet his real mother or sister until he was 18.

The couple, who live near Leipzig, claim they fell for each other when their mother died and are fighting to have the laws regarding incest changed.