R&B veteran Brian McKnight appears to have confirmed Justin Timberlake and Jessica Biel have welcomed their second child.

The couple was rumoured to have secretly welcomed baby number two back in mid-July, but the stars have yet to comment on the speculation.

Now, the singer's friend and former collaborator McKnight has suggested the news is true after casually sharing the information as he discussed how fatherhood can provide a whole new source of songwriting ideas.

In an interview with HollywoodLife, McKnight explained, "Having kids and having his family, I think he took some time to focus on those things because those things are very important.

"I think if he's gonna to do (more) music, he's going to make sure that that's secure, and then he'll bring us into his music. And being inspired!"

"He'll be inspired; he just had a new baby," McKnight said. "I think that's going to be really inspiring for him and he'll have some new music based on that, I'm sure."

Timberlake and Biel, who wed in 2012, are also parents to son Silas, five. They are said to be laying low at their home in Montana as they adjust to life as a family of four.