Jessica Biel Honors Justin Timberlake on His 40th Birthday: 'There's No One I Have More Fun with'

Lance Bass Says Justin Timberlake and Jessica Biel's New Baby Is 'Cute' — but Won't Reveal Name!

Justin Timberlake and Jessica Biel are also parents to 5-year-old son Silas

Happy birthday, Justin Timberlake!

On Sunday, the Palmer star celebrated his 40th birthday and his wife Jessica Biel marked the special day with a sweet tribute.

"There's no one I have more fun with, have more laughs with, feel more deeply for, and have more history with. I honor you today, baby. And wish you the most creative and fulfilling year to date. Happy 40th, my love," Biel, 38, wrote on Instagram, along with four of her favorite photos of the couple during their decade-long romance.

Timberlake's 40th birthday also marked his first birthday as a father of two.

Earlier this month, the singer confirmed he and Biel welcomed a second child, a son named Phineas. The couple welcomed their first child, son Silas, in April 2015.

A source recently told PEOPLE that Timberlake and Biel have been adjusting well to life as a family of four with their new baby, Phineas, and 5-year-old son, Silas. "They are spending time together as a family in both Montana and Los Angeles," said the source. "They seem happy."

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On Friday, the proud dad of two spoke about his latest addition during a virtual appearance on The Tonight Show Starring Jimmy Fallon.

"Nobody's sleeping, but he's so cute," said Timberlake, who also shared that he's been working on new music.

On Sunday, close friend Fallon dedicated a social media post to Timberlake in honor of his 40th birthday. "Everyone's talkin' it up in honor of @justintimberlake's 40th birthday!!! Love you brother. #BrothersForever #BroFor," the late-night host wrote along with a clip of the pair performing as Barry Gibb and Robin Gibb for "The Barry Gibb Talk Show" on Saturday Night Live.

Another good friend to wish Timberlake a happy 40th birthday was former *NSYNC band member Chris Kirkpatrick. "Happy 40 amigo!!! @justintimberlake we will celebrate when things get back to normal!"