John Stamos Gets Emotional As Son Billy Marks 1st Day Of Kindergarten: 'I'm Not Crying'

American actor John Stamos is getting all mushy as his only son Billy resumes his first day at kindergarten.

Billy was born in April 2018 to Stamos and his wife Caitlin McHugh, 22 years his junior and whom he married in February of the same year after two years of dating.

As little Billy marked his first day of kindergarten, the "ER" actor could not help but share the exciting news with fans while feeling sentimental about the milestone, given the duo's tight bond. 

On Stamos' Instagram Story, he announced his boy's latest feat using an adorable snap taken in a yard. Billy was captured from behind, bending to pat their black pooch and close to a black SUV. He was dressed practically in shorts, a short-sleeve shirt, socks, and sneakers while also carrying a blue-patterned backpack.

"His first day of kindergarten sporting his @poshpeanut thx," the "General Hospital" actor penned across the post, adding, "I'm not crying, you are."

Stamos never shies away from raving about his son whenever possible and even revealed last year what the boy preferred calling him.

In an October 12, 2022 episode of "Live! With Kelly and Ryan," the "Full House" star told hosts Kelly Ripa and Mark Consuelos about how well he adapted to being a dad, a role the presenters felt agreed with him.

Ripa remarked, "I have to say that in all the variations of John Stamos I've known over the years, watching you become a dad has been my favorite one." Stamos further divulged that he wept a lot with Billy before describing the youngster as the light of his and his wife's lives.

Speaking about his son was exciting for the 60-year-old as he gushed some more, disclosing the "new thing" Billy was most interested in at the time. He mentioned that the toddler was fascinated with the word "poop" and said it regularly, even in their daily conversations.

"His new thing is that he likes to say 'poop' all the time," the "Bye Bye Birdie" star shared. "I was trying to teach him a knock-knock joke," and he kept finding a way to insert the word. [He goes,] 'knock, knock?' 'Who's there?' 'Poop.'"

Stamos added that Billy often blurted out "Hi poop" despite trying to let him know that the word was not exactly fitting. In his words: "I said, 'Well, it's not appropriate to say 'poop' at school or talk about poop at school. He said, 'Well, what if I go to a poop school?' He's smart."

He then recounted a moment he FaceTimed his child, and the word came up once more but differently, directed at him. The "Fuller House" actor elaborated that while bidding Billy a good night, he told him to look at the moon. Although he was not at home with the boy that night, he promised to do the same.

Recalling the night, Stamos went on, "And then he said, 'Daddy, I can see your eyes in the moon,' and I said, 'Son, I can see your eyes too.' 

The ever-affectionate father regarded that moment as "beautiful," prompting him to tell his kid, "I love you, Billy," and in return, the preschooler heartily said, "I love you, poopy."

Stamos has often had a few things to say about starting his fatherhood journey in his 50s, admitting he is utterly "grateful" for being an old dad.

In an interview with TODAY, the "Big Shot" actor revealed,  "I'm very grateful to the gods or to the universe or whatever that I'm an older father. I couldn't have handled it earlier."  The "Born to Ride" star also admitted that he had wanted kids his whole life and always anticipated being a dad as he had TV experience with the role.

"It's the greatest blessing of my life," he further proclaimed. "I couldn't imagine my life without him, but it is challenging to do it right."

Despite having people to care for Billy when Stamos and his wife are busy with gigs, he knew how much work it took to raise a child, especially with "the way the world is right now." 

Still, he could not have chosen a better period to become a parent as he was "mature enough" and enjoyed every moment of parenting.