Mel Gibson and Oksana Grigorieva
05/19/2009 at 02:50 PM EDT
A mother always knows – even if she won't tell.
Lyudmila Chernukha, a retired Russian music teacher whose daughter Oksana Grigorieva is dating Mel Gibson, denies Oksana broke up the actor's marriage, but remains mum on rumors the pair are expecting a child.
"I can't say anything," Chernukha, speaking in Russian, tells PEOPLE exclusively from her home outside of Moscow. "Wait for the official statement from them."
Chernukha, who started her daughter on piano lesson when she was 3, said that Oksana – a singer signed to Gibson's record label – started seeing him well after the actor and his wife separated, which the mother says happened in 2006.
"He split up with his wife three years ago, so to suggest that she has broken up their marriage is rubbish," she says. "He was no longer with his wife so he was bound to meet some woman at some point, it just happened to be Oksana."
Gibson's wife of 28 years, Robyn, filed for divorce
April 13 citing "irreconcilable differences" but not stating a date when they split. Gibson says they separated in August 2006, less than a month after his notorious DUI incident.
Gibson, 53, and Grigorieva, 39, confirmed they were dating when they made a
surprise red-carpet appearance
April 28 at the Los Angeles premiere of X-Men Origins: Wolverine
amid Internet and newspaper reports that Grigorieva is pregnant. Gibson's rep has declined comment.
Grigorieva, meanwhile, has been living with her son Alexander (by her former boyfriend, actor Timothy Dalton), in a Sherman Oaks home owned by a trust linked to Gibson's production company
while working on a record. According to her mom, she has come down with acute homesickness.
"I talk to her all the time and she really misses Russia, " says Chernukha, who along with Grigorieva's father Pytor, often visits their daughter in California. "It's her homeland."