Seoul - Actor Cha Seung Won has acknowledged that he is not the biological father of his troubled son, former professional gamer Cha No Ah, his agency confirmed on Monday.

"Twenty-two years ago, Cha tied the knot with a divorcee who had a three-year-old son with her ex-husband," YG Entertainment said in a statement, reported The Korea Herald.

"He believes that the child is his own son whom he bore with all his heart," the agency added. "He made it clear that he has no regrets over the decision that he made 22 years ago."

The controversy over No Ah comes after a man filed a lawsuit against Cha, 44, claiming that the actor violated his legal rights by "pretending to be the child's biological father".

Cha is the star of K-dramas such as The Greatest Love (2011) and films such as 71: Into The Fire (2010).

For many years, his story was that he married and had a son around 1988, when he was in his late teens. The actor also has a daughter with his wife.

The agency said he is concerned about the emotional burden that his family will have to shoulder following his disclosure of his family history.

No Ah was recently charged with drug abuse. Last year he was charged with rape but the charges were dropped later.