A young man whose father has sired 40 children by 20 women is scared of unknowingly committing incest with a sibling he knows nothing about.
Video game obsessive Mike Holpin Snr, 56, has been slammed by his son– also called Mike - as "the worst man I have ever met".
Holpin, an alcoholic, has lost exact count of how many children he has sired in and around the town of Ebbw Vale, in south Wales. Many of them were taken in to care because of his father's drink problem and today shun him.
Speaking on BBC Radio 5 live, Mike Jnr revealed a consequence of his father's philandering was a risk he would discover a girlfriend was in fact a half-sister.
"When I was in school I met one of my sisters, I didn't know she was my sister," he said.
"From then, I always thought what happened if I was in a pub and met one of my sisters not knowing, because some of them haven't even got my dad's name. What happens if I went home with one of them."
Drunken knife games with his children
Recalling life at home with Holpin, son Luke revealed he was used for knife practice by his father, who would often has friends round getting drunk.
"He invented his game called 'splitsies' where you have two people standing up facing each other and he'd throw a knife at your feet to see how close he could get to your feet with hitting them," said Luke. "It seemed like a good time until my father split both sides of the trainers; I was 16. Some kids were younger."
Holpin's own hazy recollection of his own sexual conquests means he is unsure how many sons and daughter he has - or even what their names are - could be a nightmare for them.
Appearing in a Channel 5, Holpin Snr: "I don't believe in contraception and I love sex [...] I would like more kids; I will never stop."
He was unrepentant about siring so many children, but did regret missing out on their upbringing.
"Due to my drinking and my womanising, most of my kids have gone through the care system.
"It makes me feel like s*** because they've suffered. They [the social services] took them from me because I'm an alcoholic."
It means Holpin could also be one of Britain's biggest philanderers. Other parents who made headlines for having bumper families have tended to be couples in long-term relationships, such as the Radfords in Morecombe, Lancashire.