Family first.

Bill Gates and ex-wife Melinda Gates reunited for a special occasion this week—to celebrate their youngest daughter Phoebe Gates' 21st birthday. The group celebrated at the Italian restaurant Carbone Sept. 14.

Melinda wore a sleeveless, cream-colored dress paired with pink sandals and a matching purse, while the Microsoft co-founder sported a light brown sweater over a white shirt and light blue pants. The birthday girl wore a pink patterned mini dress.

"Happy birthday, @phoebegates!" Bill wrote on his Instagram that day, alongside throwback pics of the two. "You'll always be my little girl, but watching you do big things has never surprised me. I'm so proud of you."

Melinda shared on her own page a video of a FaceTime call with Phoebe, in which she gives her daughter some life advice at her request.

"You know yourself already a lot and don't ever forget who you are," she said. "And the other thing I would say is that Phoebe, you're incredibly good at making friends and knowing who your close group of friends are, your most trusted advisors, always keep those people close. That way you're never going to go wrong in life."

Melinda added, "Happy 21st birthday! I'm so proud of you and I love you so, so much."

In addition to Phoebe, Bill, 67, and Melinda, 59, also share daughter Jennifer Gates Nassar, 27, and son Rory Gates, 24.

The billionaire philanthropists have reunited a few times since divorcing in 2021 after 27 years of marriage. Both attended Jennifer's graduation from her Master of Public Health program at Columbia University, which took place in May, a month after she and husband Nayel Nassar welcomed their first baby, a daughter, who is Bill and Melinda's first grandchild.

Bill and Melinda also reunited in September 2022 at the Bill & Melinda Gates Foundation's 2022 Goalkeepers event.

"We met for the first time with our board of trustees last week in person," she told Bloomberg TV at the time. "What I think they would all tell you is that Bill and Melinda remain completely committed to this institution and to working effectively together. And that's what we're doing today."