Rob Lowe's son is all grown up!

To celebrate his 52nd birthday on Thursday, March 17, the actor took to Instagram to share a sweet photo of himself with his 20-year-old son — and John Owen is just as handsome as his famous dad in the pic!

"Celebrating my #birthday with a #workout and @johnnylowe. Whatever your age, be your best," the Parks and Recreation star captioned the shirtless selfie of the two baring their chests.

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Rob and his wife Sheryl Berkoff — who married in 1991 — welcomed John Owen in 1995. The couple are also parents to a 22-year-old son, Matthew, whom they welcomed in 1993.

Click through the gallery below to see more celebrity kids then and now!