Coming Home will be broadcast on BBC One Wales (Monday 30 November, 1930 GMT).BBC News - Prescott sheds tears for ancestor
He was moved to tears when he learned his great-great grandmother, Athaliah Parrish, bore four children while living with her widowed father, Thomas.
With the help of genealogist Gillian Smith he learns of their working 'below stairs' for the aristocracy.
But as the roots of his family tree are probed further, the secret about his maternal great, great grandmother, Athaliah Parrish, is revealed.
Ms Smith tells him: 'From what I've been told, the daughters took over the roles of the mother when they died, and they took over all the roles of the mother. It was quite common as well.'
Athaliah later married neighbour William Jones. Thomas Parrish was not invited to the wedding.
She died aged 42 in 1868. She had consumption and tuberculosis. She left 10 children."