Mel Gibson's wife filed for divorce when she learned his Russian lover was pregnant, reports the Sun. Robyn Gibson "put up with Mel for years but when she found out" Oksana Grigorieva was telling friends she was expecting, "it was the last straw," said a friend. Gibson recently moved the singer and her 11-year-old son with actor Timothy Dalton into one of his California mansions. She talked to reporters recently, apparently sporting a baby bump. Gibson had no comment.