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

Audrey Sandbank, a family therapist and author of Twins and Triplet Psychology, said the twins are likely to have felt "like soulmates" when they met for the first time because of their shared genes.

"This is a terrible trauma for them. They lost each other as babies and now they have lost each other again. They have been bereaved twice."

Pam Hodgkins, chief executive of the charity Adults Affected by Adoption, said there had been previous cases of separated siblings being attracted to each other.

"We have a resistance, a very strong incest taboo where we are aware that someone is a biological relative. But when we are unaware of that relationship, we are naturally drawn to people who are quite similar to ourselves.

"And of course there is unlikely to be anyone more similar to any individual than their sibling."