AceShowbiz - Joseph Baena put his childhood under the spotlight on his father Arnold Schwarzenegger's 73rd birthday. The son of the former California governor shared a couple of throwback photos to wish his dad a happy birthday on Thursday, July 30.

One of the snaps gives a rare look at his childhood memory as it shows his younger self being carried by the "Terminator: Dark Fate" actor. The "Twins" star looked proud as he flashed a smile while holding his son in his arms.

Another photo features Arnold on his younger and partying day, wearing a shirt which read, "Arnold is numero uno." In the caption, the 22-year-old hunk gave a sweet shout-out to his father. "Wishing the Happiest Birthday to my Dad! You are and will always be 'Numero Uno'," echoing the claim on Arnold's T-shirt.

Joseph is Arnold's son from his extramarital affair with former housekeeper Mildred Baena. He was born just weeks after Arnold and Maria Shriver welcomed their youngest son Christopher Schwarzenegger in 1997.

It's not until 2011 that news broke that Arnold fathers a child out of wedlock. The father and son have since proudly shown their close bond on social media, with the Austrian-born actor sharing photos of him attending Joseph's college graduation ceremony in April 2019.

Arnold's other children have also taken to social media to wish their father a happy birthday. Sharing throwback photos of her with her dad, including a black-and-white snap from her wedding day, Katherine Schwarzenegger wrote, "Happy birthday daddy!! I love you and can't wait to celebrate you."

Patrick Schwarzenegger, meanwhile, posted an old video in which Arnold said, "I can smoke stogies in my house. Because my father introduced me to stogies and because I'm a stud." The 26-year-old actor captioned it, "Happy birthday stud. This video pretty much sums you up... and hopefully brings a lil much needed laugh to people’s day!! love you tons."