LOS ANGELES - THE ADULT children of actor Mel Gibson are reportedly seeking lawyers to protect their interests in the divorce after rumours that Gibson's new girlfriend, Oksana Grigorieva, is pregnant.

Gibson and his wife Robyn Moore filed for divorce last month.

Twins Edward and Christian Gibson, 26, are reportedly ready to hire lawyers after Gibson told them and their siblings, that Grigorieva was expecting, said reports on Tuesday.

"In late April, Mel gathered his children at the family home in Malibu and broke the news that Oksana is pregnant, and he expects them to accept the baby as a new sibling," the National Inquirer said, quoting a friend of the actor.

"They are quite upset," the source said. "Even though Mel assured them the pregnancy was unplanned, they're furious with him and say they're going to take steps to protect their inheritance, which they feel is in jeopardy."

Life and Style Magazine, quoted another friend confirming the pregnancy.

"His wife, Robyn, is telling all her friends that Oksana is pregnant with Mel's baby," the source said.

"Robyn really doesn't understand why he wants another child at his age, but she says she knows the woman is pregnant."

Gibson says he and Moore, his wife of 28 years, have been separated for three years, reported news.com.au.