Kate Hudson can't believe how much of a ''young man'' her eldest son is becoming.

The 39-year-old actress has Ryder, 15, with ex-husband Chris Robinson, and has said she's amazed by the ''man'' he is becoming, especially when it comes to his little sister Rani, six months, whom Kate has with current partner Danny Fujikawa.

Kate - who also has Bingham, seven, with former fiance Matt Bellamy - said: ''Ryder's 15, which is crazy, I mean, it's like, I mean, he is almost, he's getting up to six feet and he's such a great boy, young man. The other day we went to breakfast and I was juggling a million things and I think it's like, really wise to go alone with three kids...and the next thing you know, I'm not eating, I'm juggling everything and I go to Ryder, [say] 'Just take Rani,' and I went to get my food at the buffet, and I looked over and here is this young man holding his sister.''

And the 'Almost Famous' star says she feels as though she has ''500 kids'', because her brood keep her constantly ''exhausted''.

Speaking on 'Live with Kelly and Ryan', she added: ''It feels like I have 500 kids. Everyone's like, 'How are you?' And I'm like, 'Exhausted. I'm so tired.''

Although she might not be in the triple digits when it comes to her children, Kate did recently admit she'd love to have at least 100 tots, despite having a ''pretty brutal'' pregnancy with daughter Rani.

She said: ''[I] would have 100 kids. [I] love being pregnant.

''[My last pregnancy was] pretty brutal. I could hardly walk. I had this thing, it happened with Bing too, I have like a dancer hip ... when I start carrying heavier, forget it, I can hardly get up the stairs.

''But I'll still get pregnant again! I just love it.''