While Simon has been thought of an unlikely candidate for fatherhood, friends and family have revealed that the TV mogul has a natural rapport with kids.
Fellow Britain's Got Talent judge Amanda Holden once told HELLO! that although Simon wants a "playboy lifestyle", he has an affinity with children, especially younger ones.
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"He's great with them. He goes on about how he doesn't want to get married, doesn't want kids… But it's a shame because he'd make a great dad."
"He asks children brilliant questions – he'll say 'Right, which one of you is the naughtiest? – and they're all so doting on him."
Amanda, who herself has two children with husband Chris Hughes, is all for Simon becoming a dad.
"I want him to have children because he would genuinely be a fantastic dad because he is good fun," the mother-of-two told the Sun. "But there is no way he would go near a nappy or a poo or anything like that."
"When the baby's walking and could have a conversation with him and know who he is, that would be fine."
Simon's mother Julie was excited to hear the news, "It's wonderful. He'll make a fantastic father," she told the Mirror.
HELLO! spoke to the British born star in March about his work with Surrey-based charity Shooting Star Chase. "Even if I didn't have what I have materially, I haven't got a sick child. I feel so much for the parents and what they go through," he said.
The 53-year-old has built many great relationships with the children, especially 18-year-old Sian Tolfree. The youngster, who suffers from a rare heart and lung disease Di George syndrome, has seen Simon's softer side.
"Simon has been my friend for years and he's lovely," Sian told HELLO!. "I text him whenever I'm going into hospital and he always texts me back straight away, no matter how busy he is."
Earlier this year, Simon told the Mirror that he would like to become a father, especially to a little girl, but was worried about staying faithful.
"Would I like kids? If I knew I could be, and how could I put this delicately, faithful, then yes. I do like kids. "I'm not sure I would be a good dad for the first six months or so but once they know who I am, I would like it.
"I definitely haven't ruled out having children."
On the subject of adoption, Simon said, "I think I'd rather have my own but then again I wouldn't completely rule out adopting either.
"If I did have a child, I have to say I'd prefer a girl."
Fans and celebrities have been keen to congratulate the pop industry magnate on his happy news.
Ex-girlfriend Carmen Electra led the outpouring of best wishes.
"I think that his child will be very well taken care and very, very loved," she told told HollywoodLife.com. "I'm going to call him as soon as… I want to know if it's a boy or girl."