The singer spoke about her fellow Britain's Got Talent judge at the launch of her first fragrance Rose Quartz on Wednesday.
''I think it will change him," Alesha told BANG showbiz. "Simon's a great guy, I think this will make him an even nicer person. Having children does change you, it makes you become a better person because you want to set an example. I think he'll be a great dad.''
The 35-year-old also spoke about becoming a mother for the first time since the arrival of her own baby, Azura Sienna, last October.
"I have been fully in the mummy zone! She has become my world," Alesha told MailOnline. "She's only 14 weeks - she smiles all the time. I haven't shown her off yet, I try and keep [her] out the limelight as much as I can. I just want to keep everything balanced.
'I don't like to be out there unless I need to be. I had some me time and stayed grounded, and now I feel energised even though I am a bit sleep deprived."
More from Parentdish