But neighbours said he was in fact celebrating because more state benefits would be given to his family - and said he had bragged about "making a fortune" on selling his story.
The man (whose identity is being kept anonymous to protect his young daughter) is now said to be in negotiations to sell his family's story to a Sunday newspaper.
But before talks with the tabloid had begun, the man said: "It’s like history repeating itself".
"I quite like the idea of being the youngest grandad in Britain, but at the same time I’m fuming that she is pregnant."
"I don't feel like a grandad. I've not got grey hair and my hearing is top notch," said the man, speaking from his home in South Wales.
The man admitted he became a father back in 1996 when he was just 14. His own mother, who is now 47, is excited about the prospect of being a great-grandmother.
"She was 18 when she had me. She was shocked when I told her the news, but she is happy now," he said.
"Her own mum is alive, and so too is her grandmother, who will become a great-great-great grandmother. There can't be too many families with six generations alive at the same time."
His daughter became pregnant by her 15-year-old boyfriend and is expected to give birth in August. The pair are both pupils at the same school and have been seeing each other for several months.
The girl’s father will be 30 at the time of the birth, slightly older than the youngest ever British grandfather, a digger driver from Warwickshire who was 29 when his son, 14, had a child in 1997.
In 2006, Tressa Middleton, from West Lothian, became Britain's youngest mother after becoming pregnant aged 11.
Previous record - Steve Smith, left, with son Dale in 1997. Mr Smith was also 29 when his son Dale became a father at age 14
Via - News.com.au , DailyMail
~ Library of weird and wonderful news blog ~