Tilda's former partner, artist and writer John Byrne, revealed he's the child of an incestuous relationship between his mother and her dad.
He says his dad gave him a 'wonderful mixture of genes' with his daughter, and claims that's what they do in Ireland, it's a traditional thing and no one talks about it.
His mother died in the '80s. She suffered from a mental illness, and he believes it was related to the relationship.
John and Tilda split in 2005 and have two children together.