Nicole Kidman wanted children ''from a very early age''.

The 49-year-old actress - who adopted Isabella, 23, and Connor, 20, with her former partner Tom Cruise, and has biological daughters Faith, five, and Sunday Rose, eight, with her husband Keith Urban - has said her maternal instincts kicked in early, and she ''always knew'' she was going to have a child.

She said: ''Because I always knew I'd adopt, I just always wanted a child. I think from a very early age, I wanted a child. I knew that I was going to have a child and that it didn't matter [how], I actually didn't know if I was ever going to give birth to a child. So that was the least of it for me. And what I did first was adopt.''

Nicole is currently starring in 'Lion', a drama about a young boy who gets lost and ends up being adopted by an Australian couple, and says she took on the role because she connected to the story about the ''bond between a mother and a child''.

She told January's issue of Vogue Australia: ''That's what I love about this movie, and what I keep trying to say.

''Once the bond is there between a mother and a child, the biological part of it is sort of the least important part. I think when that bond forms, it's astounding how powerful it is.''

And it isn't the first time the blonde beauty has opened up about the role of adoptive mother Sue Brierley either, as she previously claimed she could ''relate'' to her character's ''vision of adoption''.

She said: ''Also, there's the power of the unconditional love that a mother gives. A mother is there, whether it's Sue Brierley in the film, or me with my children.

''It's important to emphasise ... because a lot of times, with adoptive parents, people think: 'Oh, it's for other reasons.' People have said that to me; and they said it to Sue. But when it's the choice, it's just the choice. She talks about the vision she had of adopting the children; and I relate to that. It happened to me, too.''