For the first 14 years of Joseph Baena’s life, he was the dirty little secret kept by Arnold Schwarzenegger and the family housekeeper, Mildred “Patty” Baena.

The little boy didn’t even know that the former Mr. Universe was his father, until he was 13.

Describing his experience in learning that Schwarzenegger, 76, was his dad, Baena tells Men’s Health: “I remember the day very vividly…I was in the eighth grade. Fifth or sixth period. And I get called out of class to leave. And my mom’s there, and she’s like, ‘We gotta go–everyone is finding out about you and who your father is.’” Talking about the media circus surrounding his home, he continued, “I’m 13. Your body’s transforming: your mind is transforming. And now my life transformed before my eyes.”

Meanwhile, the Last Action Hero was secretly supporting Patty and his son, and Maria Shriver was unaware that the child who sometimes joined his mother at the house – playing with her children – was fathered by her husband.

But as Baena older, he started looking more like father and the secret was impossible to hold.

Describing how he lied to his wife of 25 years in his book “Total Recall: My Unbelievably True Life Story,” the star of Terminator also shares the reaction of his children when he told them of the affair.

“I asked them for forgiveness,” he said. “They cried. It tears your heart out.”

Schwarzenegger and Shriver divorced in 2021.

Doppleganger

Today, Joseph is 26 and is following his father’s footsteps as an actor and bodybuilder.

In fact, Joseph – who was on the cover of Men’s Health in 2022 – said the two bonded over fitness and his dad gave him “The Encyclopedia of Modern Bodybuilding,” co-authored by Schwarzenegger. “Even though I could call him anytime, I was too proud. I went straight to the book. I wanted to figure it out myself,” Joseph tells the fitness magazine, adding that when he was about 18, he started training with his dad, and “was so nervous…I was being observant, trying to see what he was doing and the way he was acting.”

“My dad is old-school; he doesn’t believe in handouts. He believes hard work pays off, and so do I,” says Baena. “I love the word honor, and I’m very prideful in the sense that if I use my dad’s contacts or ask him for favors, I wonder what honor is that gonna bring me?”

Joseph applies the same philosophy for his acting career and has kept his real identity quiet.

“When I go to auditions, they don’t know who I am, because we don’t have the same last name. I know it’s all me.”

The young action star has appeared in a few films with many more in production, and he also flaunted his moves in Dancing with the Stars in 2022, where he survived six episodes.

Honoring his dad, Joseph recreated the iconic “Bad to the Bone” scene from Terminator 2: Judgement Day where he plays the menacing cyborg.

While Baena is thrilled to share a strong bond with his dad, a source says “the [step siblings] don’t love Joe,” and “blame Joe for the affair.”

“I’ve been at several events where he’s brought [Baena] along,” the insider shares. “It’s not fair, but I guess it’s understandable – he’s the product of something that should not have occurred…”

FUBAR

Appearing at the premiere of the Netflix TV series, FUBAR, Schwarzenegger walked the red carpet with the four kids he shares with Shriver while Joseph walked it alone, and was left out of the family photo snapped at the event.

Posting a sole photo of himself at FUBAR, Joseph writes on Instagram, “I give FUBAR a 2 thumbs up!!!…In my unbiased opinion, FUBAR is a hilarious, action packed show that will have you on the edge of your seat the entire time!”

Fans immediately commented on his solo entrance. “Just started following to give you the type of support your snobby siblings choose not to.” Another shares, “Your half siblings have a lot of growing up to do! They envy you because you look exactly like your dad and they blame you for your dads infidelity.”

A third shares, “It’s disgusting how you are treated, man, by your own blood. Completely ignored due to something out of your control. Is it racial hostility? Who knows. At the end of the day, use this bulls*** to fuel you.”

Another netizen writes, “That’s a shame. Arnie seems [sic] to love them equally [though], if not Joe a little more because he’s walking in his footsteps.”

‘Extraordinary young man’

Though the former governor’s doppelganger and son was kept a secret for the first 14 years of his life, he admits what he did was wrong and says that Beana, now 26, “has turned out to be an extraordinary young man.”

Speaking of Joseph, the former governor says his doppelganger son is a “fantastic man” who “makes me proud.”