EXCLUSIVE: Terminator Too! Secrets of Arnold Schwarzenegger's Bodybuilding Boy's Mission to Muscle Into Dad's Territory

Muscleman Arnold Schwarzenegger's look-alike "secret" son is following in his biceps – winning his first major bodybuilding competition, RadarOnline.com can reveal.

The Terminator star's "love child" Joseph Baena, 28, recently snagged top honors in several categories at the NPC Natural Colorado State Competition.

But the prize comes as Schwarzenegger, 78, confessed the revelation he'd fathered Baena wrecked his marriage and building a father-son relationship hasn't been easy.

"It was tough on everyone," the True Lies star admitted.

RadarOnline.com was first to reveal Baena's identity in a blockbuster exclusive in 2011.

As reported, Schwarzenegger was married to Maria Shriver, a member of the politically powerful Kennedy clan, when he fell into an illicit affair with their housekeeper, Mildred Baena.

Mildred was married at the time so her pregnancy didn't raise eyebrows and she reportedly told everyone that Joseph was her husband's child.

But by the time Joseph was 8, there was no hiding the truth – Joseph looked exactly like Schwarzenegger.

"I realized there was very little doubt that he was my son," said the Total Recall star, who has four children with ex Shriver – Katherine, 36, Christina, 34, White Lotus hunk Patrick, 32, and Christopher Schwarzenegger, 28.

When a suspicious Shriver confronted Mildred, the housekeeper confessed.

Humiliated, Maria filed for divorce in July 2011, citing irreconcilable differences.

Arnold admitted the divorce brought him to his knees.

"I had personal setbacks, but this was, without any doubt, the biggest setback and the biggest failure. Without any doubt," he said.