John Stamos welcomes his very first child: 'Not just an uncle anymore!'

All that practice as Uncle Jesse is about to pay off -- John Stamos is officially a dad!

The "Fuller House" star and his wife, Caitlin, just welcomed their newborn son, Billy, named after John's late father. A black-and-white photo shows the little one snuggled up on his dad's chest.

"From now on, the best part of me will always be my wife and my son," John wrote on Instagram, adding that he's "overjoyed." "Welcome Billy Stamos (named after my father)."

See the sweet photo of John and his newborn son:

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He also noted via hashtag, "Not just an uncle anymore."

An emotional and ecstatic John wed Caitlin in February, just a few months after they'd revealed the exciting pregnancy news.

"I've waited my whole life for this," Stamos told Entertainment Tonight of finding the girl of his dreams and starting a family.

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John, 54, has openly talked about the bittersweetness of becoming a father without the presence of his own parents. “I will certainly fall short of the father my pop was, but – I’m going to give it my all," he wrote late last year.

“You know how you put your father on a pedestal, and he’s a superhero, and then as you grow older, you go, ‘Ah, he’s just a man’? I never got to that point," John has told People. "Till the day he died, he was bigger than life to me."