"We're 8 months old today, but I swear this kid is already stronger and smarter than some grown ups I know!" the proud dad bragged in the caption.
"Keep climbing my son!" he encouraged. "Mommy and daddy always got your back! #babyChmerkovskiy @petamurgatroyd #TfuTfuTfu."
The video shows Shai smiling and vocalizing as he crawls up the steps. Chmerkovskiy can be heard urging, "Let's go! Little baby lion, let's go, let's go," with Murgatroyd praising her son with "Good boy!"
Chmerkovskiy and Murgatroyd welcomed Shai in January, and married at Oheka Castle in Long Island, N.Y., in July. The couple confirmed in August that they will both compete as pros in Season 25 of "Dancing with the Stars."
"Since last season ended, we got back into, sort of like, enjoying Shai's little moments, and these moments are incredible," Chmerkovskiy said in an interview on "Good Morning America."
"Every day something new happens that is just fascinating, that makes you not want to leave the house."
"I think coming back this season ... We just wanna have fun, we just want to be a sort of family doing stuff together," he added. I want [Shai] to [dance] when he watches mommy and daddy on TV."
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