Arnold Schwarzenegger's mistress' ex-husband thought he had fathered their child.

Rogelia Baena thought the 13-year-old boy he raised with Mildred 'Patty' Baena - ex-housekeeper of the actor - was his own, and is even listed on the birth certificate as the father.

He told US show Entertainment Tonight he was "very, very angry" when he found out the 'Terminator' star was the child's real father when his sister broke the news.

Speaking in broken English, when asked how he felt when he first heard the news, he said: "No believe."

Mildred filed for divorce from Rogelia in 2008, citing irreconcilable differences, and Rogelia admitted he hadn't seen the boy in a year, but insisted: "That is my son."

He also said if he met him again, he would tell him: "I am your father. That's all."

He added: "Arnold Schwarzenegger is, for me ... was my hero. Now, I feel betrayed."

Meanwhile, Patty's family members have claimed she never told them or her son who the true father was, and they are upset with her for not telling them, especially as her mother, Evelyn Pena, was also employed by the Schwarzenegger family and her sister, Miriam Pena still is.

The family are even sympathetic toward Arnold's wife, Maria Shriver, whom is expected to file for divorce from the star, who she split from earlier this month, shortly before the revelations were made public.

A Pena family source told the New York Post newspaper: "Maria would always make sure to help us, even with little things, gifts, Christmas stuff, things like that, and now we end up making her go through this crap because of Patty. It's not cool.

"The family is not happy with Patty right now because she never told us or warned us and now we have to deal with all this attention."

Maria gave birth to the youngest of her four children with former California Governor Arnold, Christopher, 13, just days after Patty's son was born.

The couple also have also have children Katherine, 21, Christina, 19, and Patrick, 17, together.