Joseph Baena celebrated his 23rd birthday on Friday, Oct. 2. Over the birthday weekend, proud dad Arnold Schwarzenegger shared a loving message for his son on Instagram.

Arnold Schwarzenegger celebrates son Joseph Baena's birthday

"Happy birthday!" Schwarzenegger wrote, tagging Baena's Instagram account. "I love watching your progress with your training, your work, and in every part of your life. I can't wait to see what's coming next. I love you!"

Schwarzenegger's post came with an altered photo of his son DJing, signed off "love Dad." Baena is the son of Schwarzenegger and former family employee Mildred Patty Baena.

Joseph Baena is the son of Arnold Schwarzenegger and Patty Baena

Schwarzenegger's so-called "love child" was born in 1997 in secrecy, but the eventual revelation led to his and longtime wife Maria Shriver's separation in 2011. But Arnold and his son are occasionally photographed spending time together, with the lookalike pair often getting together to exercise. Such was the case on the birthday weekend, when the father and son were spotted—in Daily Mail photos—biking with a friend in California.

Baena, a fitness trainer, regularly documents his workouts and exercise regimens on Instagram — and it's safe to say he's following in his father's footsteps. 

Arnold also celebrated his 73rd birthday in July and has a new TV spy project in the works as we head into 2021.