Robbie and Ayda have a 23-month-old daughter Theodora 'Teddy' Rose and they are expecting their second child - a boy - in October.
Before stepping on stage at a recent show in Melbourne, Australia, the 40-year-old dad was rhapsodising about the joys of fatherhood.
"The most surprising thing about being a dad is what you get back," he told the Daily Mail - no doubt while offering a flash of his trademark cheeky grin."I was always terrified of the responsibility of being a father and being pinned down.
You know, I did the sex, drugs and rock and roll for the longest time and it's a lot of fun. And then a child turns up and you go right, I'm a grown-up now, but what you don't realise is how much love you get back.
"You are looking at the universe and the universe looks back at you, and it's going I love you."
In his younger years Robbie's partying antics earned him a reputation for being one of the baddest boys in pop, but he claims that since Teddy was born in 2012 he has undergone a transformation.
"[Now] I'm a daddy, and I'm married, and I have another child on the way," he said. "I'm more of a family man. You have to be when you have kids.
"It used to be sex, drugs and rock and roll. One out of three ain't bad I suppose at the moment – I'll let you guess!"
Teddy will be celebrating her second birthday on Thursday September 18. She's at the family's home in LA with Ayda, while her dad is in the middle of a tour of Australia. But Robbie will be in constant contact.
'I was on Skype with her (Teddy) this morning," he said. "And - totally unprompted, she's not even two yet - straightaway she looked at the screen and went 'I lub you daddy, come here'.
"'It doesn't get better than that."