That looked fun!

Rob Lowe's son John turned 21-years-old on Sunday, Nov. 6 — and the family celebrated his milestone birthday by taking a memorable trip to Las Vegas over the weekend!

View this post on Instagram

#birthday #vegas 21 and done!!

A post shared by Rob Lowe (@robloweofficial) on

"#Birthday #Vegas 21 and done!!" the Brothers & Sisters star captioned the snapshot of himself, his wife, Sheryl Berkoff, John and the couple's older son, Matthew, 23, at a club. Who says you can't party with your parents?!

MORE: Rob Lowe Gets Slammed at His Comedy Central Roast — See the Funniest Jokes!

Rob and Sheryl — who married in 1991 — previously welcomed John in 1995 and Matthew in 1993.

Click through the gallery below to see more of Hollywood’s cutest families!