John Travolta is remembering his late son Jett on what would have been his 33rd birthday.

On Sunday, the "Grease" star shared a touching Instagram tribute, posting a throwback photo of himself holding a young Jett in his arms as the two smile at each other, with Jett gently holding his father's face.

"Happy birthday Jett -- I miss you so much!" Travolta wrote in the caption. "Love you forever!"

Jett died in January 2009 at age 16 after suffering a seizure while the family was vacationing in the Bahamas. Travolta's attorney later confirmed that Jett had experienced seizures in the past.

The "Saturday Night Fever" actor and his late wife Kelly Preston, who died in 2020, shared two other children in addition to Jett: daughter Ella Bleu and son Benjamin.

Over the years, Travolta has often paid tribute to Jett and reflected on his son's lasting impact. In a 2021 appearance on Kevin Hart's talk show "Hart to Heart," he recalled a heartfelt moment with his youngest son Benjamin, who once expressed fear of losing his father, after his mother's death.

PHOTO: Celebrity Sighting In Paris November 3,2008 — John Travolta is seen leaving the 'Relais Plaza' restaurant with his daughter Ella Bleu Travolta, his son Jett Travolta and his wife Kelly Preston, Nov. 3, 2008 in Paris, France. Marc Piasecki/GC Images via Getty Images

"I said, 'Well, it's a very different thing.' And I went through the differences about my longevity and her limited life," Travolta said at the time.

He said he told Benjamin then, "You know, Ben, you always love the truth, and I'm gonna tell you the truth about life. Nobody knows when they're gonna go or when they're gonna stay… Your brother left at 16 -- too young. Your mother left at 57 -- that was too young. But who's to say? I could die tomorrow. You could. Anybody can. So let's look at life as part of life. You don't know exactly -- you just do your best at trying to live the longest you can."

Travolta previously honored Jett with a birthday tribute in April 2024, posting a sweet throwback photo of himself, Jett and Preston at the time, along with the caption, "Happy birthday my Jetty - not a day goes by where you're not with me!"