The unnamed lad was born on August 20,1997 by caesarean delivery at the island's Princess Elizabeth Hospital to Dawn and Raymond Brooke.
The details of Brooke's son have emerged after 10 years of the boy's birth only after the family spoke about it.
"People are generally not quite aware of the extreme good luck we had at our age. We're overjoyed to have our son. We've been hugely fortunate. He's such a fantastic boy. We've kept it quiet," Telegraph quoted Raymond Brooke, as saying.
Nick Otway, Dawn's son from an earlier marriage, said that the birth of the boy has brought immense happiness for his mum and step dad, and that they are all happy for that.
"When they told us we all gave Ray a round of applause. He and mum are both extremely healthy and active and having a youngster to bring up is now a large part of that," he said.
"It's brought them both a tremendous amount of happiness. There are women who get to 40 or 45 and think, 'I'm far too old to have a baby.' This should give them some reassurance to know they're not." "My mum and my stepdad make a fantastic couple. And Ray has so much fun with the lad. They're extremely close."
"They're both heavily into Harry Potter. The boy is extremely creative and mathematical as well. He's a jack of all trades really. Ray's been reading to him for years. Now the lad's got a phenomenal IQ. I think he'll do extremely well in later life."
According to Guinness Book of World Records, the oldest mother is Adriana Iliescu who gave birth to a daughter in 2005 when she was 66 years and 230 days.