Sir Elton John doesn't want his son to be an only child.

The 'Rocket Man' singer - whose boy Zachary was born on Christmas Day 2010 via a surrogate mother - says he and husband David Furnish would love another baby because they think it's important for Zachary to have a sibling.

Elton - who, himself, is an only child - said: ''I spent it in my room, listening to music if my parents were arguing. I think it's difficult to be an only child, and to be an only child of someone famous.

''I want him to have a sibling so he has someone to be with.''

Elton - who performed at last night's (04.06.12) Diamond Jubilee concert, to celebrate Queen Elizabeth's 60 years on The Throne - also wants Zachary to have a sibling because he knows it's going to be hard for him growing up with two fathers.

He told The Guardian newspaper: ''I know when he goes to school there's going to be an awful lot of pressure, and I know he's going to have people saying, 'You don't have a mummy.' It's going to happen. We talked about it before we had him. I want someone to be at his side and back him up. We shall see.''

The 'Your Song' hitmaker also revealed how the couple try not to spoil Zachary too much despite being very rich.

He said: ''At Christmas we bought him a swing for the garden and a little slide, and this was his Christmas present and his birthday present from us. But he had so many presents from other people throughout the world, which is touching, but we actually found it obscene.''