Harding, 35, said Cheryl had been “broody for years” and that she was always very “maternal”.
Speaking to OK! she said: “I’m really happy for her. Cheryl has been broody for years. I think she’s wanted a baby since Kimberley [Walsh] first fell pregnant
“Cheryl has achieved a lot in her career but becoming a mum was always her ultimate goal. She’s been through a lot so I’m glad Cheryl’s got her happy ending with Liam. She has always been very maternal.”
The couple shared the news on Instagram with a picture of Payne holding their son and told fans that they were “overwhelmingly happy”.
Harding addressed the 10 year age gap between the couple and defended them against critics.
“I don’t know Liam but he seems like a nice guy,” she said. “I know some people were surprised by the age difference but I don’t see what the fuss is about.
“There’s nothing wrong with a little age gap, especially when you get to our age.”
Cheryl and Payne were intensely private throughout the pregnancy and never confirmed the news until February, when Cheryl posed with her baby bump for a L'Oreal and Prince's Trust campaign.
The couple are reportedly keen to keep their child out of the spotlight.
“They've always been a very private couple and they want their son to remain private as well,” a source told the Daily Mirror. “They don't want him to be in the spotlight at all.
“They want him to grow up away from the cameras.”