Estranged Husband Of Arnold's Mistress Thought Schwarzenegger's Child Was His

Even though Arnold Schwarzenegger is the biological father of Mildred "Patty" Baena's youngest child, the housekeeper's estranged husband, Rogelio Baena, thought he was his dad.

Mildred Baena gave birth to her son with Schwarzenegger five days before Arnie's wife Maria Shriver gave birth to their son Christopher in 1997. Baena was married to Rogelio during this time and was listed on the child's birth certificate as the biological father. But Rogelio tells Entertainment Tonight he found out only last week that Arnold was, in fact, the real father.

In an interview with ET, Rogelio says he and Shriver were "betrayed:"

“Arnold Schwarzenegger for me, [was] my hero... Maria is destroyed.”

Mildred filed for divorce just three years ago -- and Rogelio has not filed a legal response, so the divorce has yet to be finalized.

The heartbroken father also said he would like to tell the now-teenager, “I am your father. That’s all.”

The full interview with Rogelio will air as a two-part interview on ET Tuesday and Wednesday night.