She told Women's Health UK magazine: ''Kim is lovely. I'll email her and she gets right back to me. It makes me feel like garbage because I'm like, 'I'm 10% as busy as you and I don't get back to people.'
''They are the most beautiful family. I look at them and think, 'How do I get this?'''
Meanwhile, the 29-year-old beauty previously revealed she'd love to have children as she wants a beautiful body like pregnant mum-of-one Kim.
She said: ''We want a lot of kids. I would love to have three or four of my own, and then adopt a few. So basically I'll be pregnant the rest of my life.
''You look at Kim and see how women's bodies just become so beautiful. [The thought] of getting boobs thrills me. And John loves pregnant women.''
And John, 36, wouldn't mind if they had a baby girl as he thinks he's ''good with women'' because of his job as a musician.
He added: ''I'm attracted to the heightened femininity.
''I'm a musician, I'm good with women and I'm a feminist, so I think I'll be a good 'girl daddy.'''
His new album Underneath It All is out now.