Katherine Heigl would like to have two more children.

The 36-year-old actress already has daughters Naleigh, six, and two-year-old Adalaide with her husband Josh Kelley and she's keen to add a couple more to their brood, but she's determined to do it sooner rather than later because she's worried about her age.

Speaking in the March issue of Australia's InStyle magazine, she said: ''I would love two more kids. Josh is sort of considering oe more. But I'm getting older! I met a woman the other day who had twins at 49, and I went, 'How do you do it?' I'm tired now. At 49, I wouldn't have the energy.''

However, the blonde beauty has admitted she doesn't want her children to follow in her footsteps and become actresses.

She explained: ''My daughter just came home with a project from school; she was asked what she wants to do when she grows up. She said: 'I want to be a musician like daddy and act in movies like mummy.' I went, 'We're so screwed!' I'm happy to support it when they're adults but I don't want to schlep them around to auditions and do all the stuff my mum had to do with me.''

Meanwhile, Katherine tied the knot with Josh in 2007 after dating him for two years and she believes their marriage gets better and better as the years go on.

She said: ''It's better than it's ever been. The first year we struggled - you're adapting to marriage and suddenly the stakes are much higher. It's not like you can just break up ... Josh has become my best friend.''

She added: ''His level of support and loyalty are amazing. He is a kind person and he makes me better. I look at Josh and I think, knock on wood, 'We'll make it.' ''