He continued, "Welcome Billy Stamos (named after my father) #NotJustanUncleAnymore #Overjoyed".
John Stamos and Caitlin Stamos made headlines when they married shortly after announcing Caitlin is also pregnant with John's first child. John Stamos and wife Caitlin McHugh have welcomed their newborn son.
The couple confirmed the pregnancy in December. They had met filming an episode of Law & Order: SVU in 2011, but only started dating a few years later after reuniting on the set of Fuller House. The couple got married in Beverly Hills on February 3.
John, who was previously married to Rebecca Romijn, admitted past year he'd always wanted to be a father and felt it would be a "tragedy" if he never had kids.
"I'll be a fun dad". Then I said, I better have a ring on her finger because it's the right thing to do, and I wanted to marry her anyway. "I'll probably just do all that stuff", he joked.
She described it as the look of a man who wanted to be a father his whole life but thought the moment had passed. "So I called her parents to ask, and it was like, 'You better!'" Every day I say, 'You're doing so great, you're doing so great'.