Justin Timberlake keen for baby number two

Actress Jessica Biel and musician Justin Timberlake. Photo / Getty Images

Justin Timberlake hasn't ruled out the possibility of having another child.

The Can't Stop The Feeling hitmaker welcomed son Silas Randall into the world 18 months ago with his wife Jessica Biel and quipped he was "having a lot of fun practicing" to have another child.

Speaking to Extra's Mario Lopez on the Los Angeles premiere of Trolls, he said: "Silas is a year and a half ... want him to stay that size."

And asked if he would be adding to his brood, he added: "I'm having a lot of fun practicing."

Meanwhile, the 35-year-old singer previously revealed becoming a father has "changed everything" for him.

Musician Justin Timberlake. Photo / AP

He shared: "It changes everything. You literally wake up and look in the mirror and go, 'I have no idea what I'm doing!'

"It's crazy. This new appreciation for both of them, her and him, it's humiliating and it's humbling at the same time ... You watch her realise she has a gear she [thought she] didn't have and then you go, 'Woah, yeah.' ...

"I would have never written a song like Can't Stop the Feeling! [if I wasn't a father]. I don't know that it was directly inspired to be something that my son could listen to of mine, because there's a lot of music he can't ... at least not yet ... [but he was an influence]."

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FLEXIN' on Fathers Day... #HappyFathersDay to ALL of the Dads out there from the newest member of the Daddy Fraternity!! --JT

A post shared by Justin Timberlake (@justintimberlake) on Jun 21, 2015 at 9:11am PDT

And Justin feels he has a different outlook on life since his son arrived.

He added: "I'd be leaving out the whole truth if I didn't say having him shaped what the song actually is. [Having a child] gives you a different insight. It's like The Matrix, man. You open a door and there's this whole other world on the other side of it. And you look back through the door at the other world and you're like, 'What was I doing there?'"

- Bang! Showbiz