Nick Jonas is all grown up!
The singer celebrated his 21st birthday in Las Vegas over the weekend alongside girlfriend Olivia Culpo and bothers Joe and Kevin Jonas.
Nick's B-day festivities began Saturday night at the Wynn Las Vegas, where he, Joe and Kevin enjoyed a meet and greet with the cast of Le Reve—The Dream.
After that, the trio was joined by their respective significant others (Joe with girlfriend Blanda Eggenschwiler and Kevin with wife Danielle Jonas) for a family dinner at Andrea's.
Nick and Culpo "were very playful and cuddly throughout the meal while Kevin was doting on his expecting wife, Danielle, the entire time," a source tells E! News. The restaurant provided signature chopsticks with their names engraved on them at the table. They shared several sushi rolls including crispy tuna, special cucumber roll, spicy tuna shrimp tempura, lettuce cups, New York Strip steak, miso black cod, Jidori chicken and the restaurant's signature smoked salmon.
On Sunday, the JoBros played golf and watched football before gathering with 25 of Nick's family members and friends for dinner at Botero, the steakhouse at Encore, around 10:30 p.m. The entourage split several sides, including truffle macaroni & cheese, ricotta gnocchi and wild mushrooms..
At exactly midnight, Nick was watching his iPhone's date change over to officially ring in his birthday.
The group erupted in applause as a birthday cake was presented by the staff.
The brothers sang "Happy Birthday" and Culpo snapped pictures of her man on her phone for social media. The couple cozied up for a cheers with a celebratory glass of champagne followed by a sweet kiss.
Fifteen minutes after turning 21, Nick led the group to the red carpet at XS nightclub, where the brothers all snuggled up to their significant others.
While partying inside the nightclub, a second Vegas-inspired birthday cake was brought out by the XS waitresses.
The group partied into the early hours of the morning in honor of the monumental celebration.