The GB athlete and his girlfriend Susie Verrill welcomed their first child together, believed to be a baby boy, yesterday (20 October).
Confirming their happy news, Greg shared a super-cute photo of his new arrival clutching onto his hand.
Alongside his picture, Greg wrote: "Happiest day of my life." Aww!
Greg announced he was going to be a dad six months ago. Revealing his news in a similar fashion, he took to Instagram and shared a photo of himself and Susie holding onto a copy of their baby scan.
Captioning his photo, Greg said: "We're having a baby!! #baby."
Speaking ahead of his newborn's arrival last month, Greg told the Daily Mirror he was hoping the tot would help to boost his athletic career.
Claiming he thinks he will perform better after becoming a dad, Greg said: "They call it the nappy factor... Most athletes have said to me that you stop worrying about the little things in training..
"You have another reason to relax, enjoy and have a bit more fun. Having a little one around will make it that bit more special."
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