Sir Elton John says it will be “heartbreaking” when the boy being raised by him and his gay civil partner David Furnish discovers he has no mummy.
But he says the young child is happy at the moment and “you have never seen two more contented people as David and I”.
Sir Elton was referring to the challenges that his son, Zachary, will face growing up with two male parents.
Zachary was born in America in 2010 via a surrogate woman.
In an interview with an American TV show, Sir Elton said: “I’d love to have more children.
“I want [Zachary] to have a brother or a sister to go to school with him, and so that he can have someone to play with.
“It’s going to be heartbreaking for him to grow up and realise he hasn’t got a mummy.
“But he’s so happy. I’ve never seen a more contented child. And you have never seen two more contented people as David and I.”
Counsellors have advised Sir Elton to make a scrapbook for their son that explains how he was created.