(Cover) - EN Showbiz - A secret DNA test conducted over ten years ago proved Arnold Schwarzenegger fathered his lovechild, it has been reported.

The actor-turned-politician had an affair with his housekeeper Mildred Baena which resulted in her having a son who is now 13.

Sources claiming to be close to Mildred have told RadarOnline that Arnold knew early on that the child was his but his former employee wanted him to take a test to prove he was definitely the father.

The Terminator star was allegedly desperate to keep his illegitimate child a secret but finally gave in to Mildred's demands.

"Arnold knew all along that [the boy] was his child. But Mildred insisted on a DNA test - and it proved that Arnold was the father," the source told the website.

The 63-year-old has reportedly been making secret payments to Mildred over the years. It is alleged he put down a $65,000 down payment on her family home less than a year ago, which is where she lives with the boy and her other three children.

Arnold's estranged wife Maria Shriver has now hired powerful Los Angeles lawyer Laura Wasser, sparking speculation she has decided to end her 25-year marriage.

She has also reportedly hired a private investigator to delve into the private and business affairs of her estranged husband.

Maria wants to find out about Arnold's past life, his finances and if he has fathered more children outside of their marriage.

"Maria is leaving no stone unturned and she has authorised a private detective to gather personal and business information about Arnold," an insider told RadarOnline. "Maria needs and wants to know exactly what she is dealing with."

Although Maria is distraught at her husband's infidelity she reportedly does not want their four children to hold a grudge against their father and wants them to "forgive" Arnold.

"As hurt as she may be, she will encourage them to forgive their father," a family source told Us Weekly.

The insider added that Maria's "faith and her focus on family" is getting her through this difficult time and she is "moving forward and counselling her kids".

The couple have four children: Katherine, 21, Christina, 19, Patrick, 17, and Christopher, 13, who was born just five days before Arnold's lovechild was born in 1997.

Meanwhile, Sharon Osbourne has waded into the controversy and couldn't resist giving her opinion when asked what her advice was for Arnold.

"Find a new housekeeper," Sharon joked to photographers. (C) Cover Media