They confirmed the arrival during a virtual appearance on The Ellen DeGeneres Show, which will air on Monday.
The 39-year-old singer said: “He’s awesome and so cute. Nobody’s sleeping.
“But we’re thrilled. We’re thrilled and couldn’t be happier. Very grateful.”
The couple had their first son named Silas in April, 2015 following their marriage in 2012.
Justin said the pregnancy was kept secret apart from immediate family and very closed friends that knew about it.
When asked about what it was like being a parent to two children compared to when having just one.
The singer joked: “We don’t see each other anymore.
“It’s a lot of fun. I guess the saying goes go from a zone defense to a man-to-man really quickly. It’s great. Silas is super excited.”
So, how is the five-year-old Silas adapting to being a big brother, Justin said: “Right now he’s very much liking it.
“Phin can’t walk yet or chase him down, so we’ll see what happens.”
When asked whether Silas will like to be a musician, the singer revealed that Silas was getting in video games and he’s developing into a little gamer.
He added: “But he’s into Legos and tennis. We got him a Nintendo Switch. It’s just like, child crack.”
Justin also said that Silas loves to golf just like hm, he revealed: “He likes golf, but I’m not pressing it.
“I want him to like it if he likes it. He’s fast and active so he’s very good at tennis.”