John Stamos proudly showed off his newborn son Billy to his Full House costars Bob Saget and Lori Loughlin in an adorable Instagram photo

The Full House family just got fuller!

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Stamos, 54, shared a photo of the adorable moment on Instagram Thursday in which he held Billy in his hands as Saget and Loughlin bent over him and smiled.

Billy, whose back was turned toward the camera, wore a black onesie that read “Jesse and the Rippers,” a reference to the band that Stamos’ character, Jesse, plays in.

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“The Tin Man, Dorothy and The Scarecrow say hi to the cutest of Munchkins. #BillyandtheRippers,” Stamos wrote in the caption.

Saget, 61, shared the same photo on Instagram, writing, “~ So much love John. Most beautiful boy and Mommy & Daddy ever. So proud to be a new Uncle/Tin Man, my brother.”

Stamos and his wife, Caitlin McHugh, welcomed Billy on April 10 in Los Angeles. His full name is William Christopher Stamos after the actor’s late father.

The actor announced his son’s birth on Instagram six days later, sharing a black and white photo of Billy lying on his chest with the caption, “From now on, the best part of me will always be my wife and my son. Welcome Billy Stamos (named after my father) #NotJustanUncleAnymore#Overjoyed.”

He told PEOPLE in late April being a father has changed his life.

“I cry a lot,” Stamos said. “It’s more beautiful than anyone told me it would be. I’ve been waiting a long time.”

Image zoom Caitlin McHugh and John Stamos Caitlin McHugh Instagram

Asked who Billy looks like, Stamos was torn.

“He’s got my wife’s legs, which is good,” the “Forever” singer said. “I think he’s got some good hair going. But they say it’s going to fall out and come back. I don’t know… ”

RELATED VIDEO: John Stamos on Why He’s Finally Ready to Be a Dad at 54

Stamos and McHugh got engaged at Disneyland in October, just two months before they announced their pregnancy news exclusively to PEOPLE. The couple had been dating for two and a half years. They then tied the knot and headed to Disney World for their honeymoon in February.

He opened up about fatherhood during a visit to On Air with Ryan Seacrest, telling Seacrest he was excited about naming his son after his “hero” father.