The 'So Macho' singer - the former girlfriend of 'The X Factor' boss - is confident the music mogul will live up to his title of a doting dad because he jokes around with her children, Magdalena, eight, and Zac, six, and even has the nickname ''Silly Simon.''
Speaking to The Sun newspaper, she said: ''Simon does everything naughty. I'm trying to promote eating nicely, speaking nicely, not being rude.
''He shows them food in his mouth when he's eating and gives them loud toys to bang in the bedroom when I'm trying to sleep. He's great with kids. He becomes a third child.''
The 53-year-old star - who is expecting his first child with married lover Lauren Silverman - has been keeping a low profile since the paternity scandal broke three weeks ago, but is keen to support the mother of his unborn baby while she works through her messy divorce from Andrew Silverman.
Simon will reportedly pay out $20,000 a month on a luxury apartment in New York City while Lauren sorts through the custody arrangements over her seven-year-old son, Adam.