The woman who had Arnold Schwarzenegger's secret love child has spoken about the affair, saying her son only learned about a year ago who his father was.

Mildred Baena, former housekeeper to movie star and ex-California governor, has kept a low profile since the revelations of the affair emerged.

The scandal exploded into public view after Schwarzenegger and wife Maria Shriver announced in May that they were splitting up after 25 years of marriage.

Then came his admission that he fathered a child with a member of the household staff.

In an interview in Hello! magazine, Ms Baena said that when her now 13-year-old son, Joseph, learned who his father was his response was simply: "Cool!"

The mother and son posed for the magazine in one of the first published pictures of Joseph - both with slight smiles.

She said she was not initially certain Schwarzenegger was the father but started to see a resemblance in her son as Joseph grew older.

"It became more apparent as time went on," the former housekeeper said. "I knew Arnold was the father, and maybe as Joseph got older and began to look like him, he (Arnold) wondered. But he never said anything to me."

She said Ms Shriver also grew suspicious as whispers circulated in the household over the similarities between Joseph and her boss. Ms Baena said Ms Shriver finally asked "point blank" if the boy was Schwarzenegger's son, and was "so strong" when faced with the truth.

"She cried with me and told me to get off my knees," Ms Baena said. "We held each other and I told her it wasn't Arnie's fault, that it takes two."

Schwarzenegger has put his Hollywood comeback on hold to sort out his personal life in the aftermath of the scandal, and Ms Baena stressed that the former governor was "a good man."

"I know he's suffering too," she said. "He loves Maria. I hope with time they work things out."