Rod Stewart's children are his ''fountain of youth.''

The 'Maggie May' rocker has eight children with his youngest kids being Alastair, seven, and two-year-old Aiden, with his third wife Penny Lancaster.

Rod, 68, insists his two young sons keep him active and keep him feeling young.

He told the new UK issue of HELLO! magazine: ''Alastair comes home from school and says, 'Dad, let's go!' I have a stretch and go play. If there's a fountain of youth, its children.''

Penny, 42, adds that Rod has a number of different roles to play to each of his children which also include grown-ups Sarah Streeter, Kimberley, Ruby, Renee and Sean and Liam, 19.

She added: ''They all require a different dad, as he puts it. The older kids want career advice, and to talk about their relationships, the younger ones' needs are all about school, while Alastair is, 'Dad, come and play football,' and Aiden is, 'Come and roll around on the floor with me.'

''He has two personalities anyway - the rock star on stage then the husband and father, so he is able to morph himself into quite a few different roles. He's close to all his kids, which is great.''

Penny is also moved by Rod's tribute to his children on his latest album, 'Time'.

She said: ''The last song, 'Pure Love', is tear jerking. It's basically about all of his children and how he'll always be there for them. It always brings a lump to my throat ... You want your children to know what your life was like when you were younger. When He's 90 or 100 he might not remember so it's good that it's committed to paper now.''