John Stamos. Picture: Instagram

John Stamos and his wife Caitlin McHugh have welcomed their first child, a son named Billy, into the world.

The 'Fuller House' actor and his wife Caitin McHugh have welcomed a son into the world and have named the youngster in honour of the 54-year-old star's beloved late father, Billy.

John - who is best known for playing Uncle Jesse in 'Full House' and 'Fuller House' - revealed the happy news on Instagram by sharing a black and white photo of the baby resting on his chest and clutching his finger.

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He captioned the image: "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 (sic)"

John, who was previously married to Rebecca Romijn, admitted last year he'd always wanted to be a father and felt it would be a "tragedy" if he never had kids.

He previously said: "It's just taken me a lot longer than I anticipated.

"It would be a tragedy if I didn't have children and I finally found the right woman -- the perfect woman. I know my parents are smiling down. I know they would love her. She's a gentle, kind, graceful soul who would be a good mother."

And the former 'E.R'. actor previously praised Caitlin - who he married in February - for dealing with her pregnancy "like a champ".

He said: "She's so beautiful pregnant. She's so magical.

"She is the most graceful person I've ever met in my life, and she's handling pregnancy like a champ. Every day I say, 'You're doing so great, you're doing so great.' 

"Just every day I'm with her I just realise, first of all, how lucky I am, but what a special human she is. She's magical. She floats into a room. I've never heard her say a bad word about anybody."

John also insisted he doesn't have any nerves about becoming a dad.

He said: "I'm not nervous at all. I've been not nervous about getting married - I just knew it was the right thing. I'm not nervous about having a kid, I'm not nervous about having a kid with her."