"Happy 20th Birthday to @julianseinfeld! Your work ethic enables you to balance a heavy college course load with a job you love," she wrote on Instagram. "Your sharply tuned BS detector suffers not one fool. The moral high bar you set for those around you keeps us all in line. You chose your friends wisely, and treat them all like family."
"You are such a phenomenal and gorgeous human being. Your goodness is greatness, especially in this world today," she continued. "I love you, my sun."
Jerry added his own message in the comments writing, "We love you so much, Jules. Happy Special Birthday this year!!"
Jerry Seinfeld and his wife Jessica celebrated their son Julian's 20th birthday on social media. (Instagram: Jessica Seinfeld)
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Jerry Seinfeld and Julian Seinfeld attend a Brooklyn Nets game. (Getty Images)
Julian currently attends Duke University along with his sister Sascha Seinfeld.
The comedian has previously admitted his kids do find him funny, just not all the time.
"But if I'm not, which occasionally, of course, humor is a very hit-and-miss business, as we know. And when I'm not, believe me, they will take me out at the knees," Jerry told NPR in a 2020 interview. "They will. They'll look at me and just go, 'That's it? That's all you got?'"
The "Seinfeld" star also claimed he's "very hard" on his family when it comes to humor.
"Kvetching is only of value if you can do it in an amusing way," he says. "My son just came in a minute ago and he says, 'I can't study. The wind is howling.' I said, 'We can't say things like that.' If you're going to complain – my whole act is, of course, constant complaining – but you have to find something amusing in that complaint. Otherwise, keep your mouth shut."
"I'm very hard on my family as far as being entertaining. You know, at my dinner table, you're supposed to be funny."
Jerry Seinfeld and Jessica Seinfeld share three kids together, Sascha, Julian and Shepherd. (Getty Images)
Jerry Seinfeld and Jessica married in 1999. (Getty Images)
Jerry and Jessica married in 1999. The couple first met at a Reebok gym in New York City, the former fashion publicist told The New York Times. At the time, Jessica was already married to producer Eric Nederlander.
Eventually she ended her marriage to Nederlander and tied the knot with Jerry roughly a year after they began dating.
Jerry and Jessica share three kids together. The couple welcomed their daughter Sascha in November 2000. By March 2003, Jessica gave birth to Julian. They completed their family with the birth of Shepherd in August 2005.