Mark MacDonald had always known he was adopted and was comfortable with it - but when he and his wife Tina found they couldn't safely have children of their own, he went looking for his birth family. After reaching out through adoption agencies, he quickly established a close relationship with long-lost sister Rachel Elliott, and - over a family dinner - a life-changing offer was made. Mark and Rachel have written a book together called Love & Genetics: A true story of adoption, surrogacy, and the meaning of family. Get in touch: [email protected] Presenter: Mobeen Azhar Producer: Laura Thomas and Tom Harding Assinder (Photo: (L-R) Mark, Rachel and Tina with the twins. Credit: Mark MacDonald)