Mel Gibson’s girlfriend Oksana Grigorieva is pregnant, according to reports from the US.

The National Enquirer and Life & Style magazine are both reporting that the 39 year old Russian singer is expecting Mel’s baby later this year.

A source told the National Enquirer that Mel broke the news to his family just weeks after his wife of 28 years Robyn filed for divorce: “In late April, Mel gathered his children at the family home in Malibu and broke the news that (his girlfriend) Oksana is pregnant, and he expects them to accept the baby as a new sibling.

“The pregnancy was unplanned.”

Another source told Life & Style: “Robyn is telling all her friends that Oksana is pregnant with Mel’s baby.

“Robyn really doesn’t understand why he wants another child at his age, but she says she knows the woman is pregnant. I get the impression Robyn confronted Mel about it, and he admitted it.”

Mel is believed to have started seeing Oksana late last year, after separating from Robyn in the summer 2006. The baby will be Mel’s eight child - and his seven children with Robyn are said to be upset about the impending arrival of a new half-sibling.

The National Enquirer’s source added that Mel’s oldest sons twins Edward and Christian have hired a lawyer to look into protecting their trust funds: “They are quite upset… they’re furious with him and say they’re going to take steps to protect their inheritance, which they feel is in jeopardy.”

Mel is worth an estimated $900million, with Robyn theoretically entitled to half of the fortune under California marriage laws.