Fans Say Mark Ruffalo 'Cloned Himself' in Rare Photo With Grown Son

Mark Ruffalo is celebrating his eldest turning another year older!

Keen Ruffalo marked his 23rd birthday on Wednesday, June 19, and the Avengers alum was front and center to honor his little "clone," as fans are calling him, with a handful of rare snapshots uploaded to social media.

The carousel began with a sweet childhood photo featuring Keen standing in a field of flowers almost as tall as he was, showing off some shaggy blonde locks that darkened as he aged.

In the next two snaps, father and son posed together, followed a few slides later by a much more recent side-by-side of the two, with Keen rocking his father's signature dark curls and Mark's looking a little grayer.

"Happy Birthday, Keen," the actor captioned the photoset. "Love you so much and proud of all you have accomplished this year. Keep going."

Fans were stunned by the power of the Ruffalo genetics, with one writing, "Wait, he cloned himself. Happy birthday!"

"Absolutely so twinning!!!" someone else agreed, while another admitted to having had to take a doubletake. "I literally had to look again," they wrote. "Cloned himself ❤️."

"Your doppelgänger!" another declared.

Of course, Mark is also the doppelgänger of his own father, Frank Lawrence Ruffalo, as proven by his Father's Day tribute from earlier this week—and every other photo of the two ever taken.

"lookin just like your daddy," one fan wrote at the time, while another celebrated, "He raised a good man."

Mark and his wife, Sunrise Coigney, also share 19-year-old Bella and 16-year-old Odette.

Next: Mark Ruffalo's Larger-Than-Life Hair in Throwback Photo Sends Fans Into a Frenzy