It was reported back in July that the couple, who also have five-year-old son Silas, had quietly become parents for a second time, but the showbiz pair remained silent on the rumours.
However, while filming an interview for The Ellen DeGeneres Show – airing on Monday – Justin confirmed the happy news.
“He’s awesome and so cute. Nobody’s sleeping,” he gushed. “But we’re thrilled. We’re thrilled and couldn’t be happier. Very grateful.”
The SexyBack star also joked that he and Jessica “don’t see each other anymore” now they have two kids, but added that it’s a “lot of fun”.
As for how Silas is coping with being a big brother, Justin smiled: “Right now he’s very much liking it. Phin can’t walk yet or chase him down, so we’ll see what happens.”
Justin and Jessica wed in 2012.
They were rocked by rumours all wasn’t well in their marriage in late 2019, when Justin was spotted out drinking with his co-star, from upcoming drama Palmer, Alisha Wainwright, and she had her hand placed on his knee as they enjoyed a boozy evening in New Orleans.
Justin, 39, then issued a public apology to 38-year-old Jessica: “A few weeks ago I displayed a strong lapse in judgment but let me be clear nothing happened between me and my costar. I drank way too much that night and I regret my behavior. I should have known better.
“This is not the example I want to set for my son. I apologize to my amazing wife and family for putting them through such an embarrassing situation, and I am focused on being the best husband and father I can be.”