Rob Lowe's son trolls him on Instagram any time he posts a selfie

Well done, Johnny.

Rob Lowe is beloved by millions of fans across the globe. But there is at least one person in his life who happily brings the star back to earth.

Johnny Lowe has built a reputation on Instagram for his pointed comments immediately after his dad's selfies go live.

Case in point: this week, the actor posted a sweaty, post-workout picture along with the words: "If you’re not wet from your workout, you’re probably not working hard enough!"

Johnny was quick with a rejoinder: "The subtle art of taking a selfie in front of ur Emmy nominations."

His reply got a whopping 3,700 likes ... which is quite a few for an Instagram reply.

Exhibit B -- Last week, Lowe posted a pic with his son and Chris Pratt.

"Threesome," Lowe wrote.

"I don’t condone this caption," Johnny replied.

And the hits keep coming.

Lowe posted a topless pic at the beach and wrote, "Weekend."

Johnny replied, "Plz god no."

You are getting the point.

It's not all snark between father and son -- even if the posts still stay far from cloying.

The elder Lowe recently wrote a post saying: "Testing out the swing and mustache at Pebble, @johnnylowe says it’s a no go. Thoughts?"

The response was quite sweet: "Tbh I’m just jealous cause i can’t grow one."

He picks his battles, that Johnny Lowe.