After raising his sons for 20 years, a UK businessman has revealed he found out that the young men were not his own.

Richard Mason, co-founder of price comparison site Moneysupermaket.com, found out in 2016 that he had been infertile since birth.

A doctor gave Mr Mason the doubly tragic news - not only did he have cystic fibrosis, a life limiting genetic condition, but his wife had cheated on him, as men with cystic fibrosis are unable to father children.

Further DNA testing confirmed that his three sons were not his. Mr Mason immediately began legal action against his wife to get back money from their divorce settlement.

He also sued her for paternity fraud.

His wife, Kate Mason, has agreed to repay £250,000 (NZD $473,500) of their £4 million divorce settlement.

However, she will not identify her lover, leaving Mr Mason to appeal to the public for information on the biological father of his sons.

"They will want to know who their real father is, even if hopefully they will always think of me as their dad," he told the Mail on Sunday.

Mr Mason is now no longer in his sons' lives, saying the legal battle with his ex-wife left his relationship with two of the boys broken.

"I still see what the boys are doing on Facebook and it's heart-wrenching because we saw the graduation of the eldest on there but I wasn't invited"

He told the Mail on Sunday that "If I could wave a magic wand, I would want to be in all their lives."

Newshub.