Mary Kennedy — Still Married to Robert Kennedy Jr. at Time of Death

Mary Kennedy was legally married to her estranged husband Robert Kennedy Jr. at the time of her death … our sources has learned.

RFK Jr. had filed for divorce back in 2010 … but according to court records, the divorce proceedings were still in progress … and the judge had NOT yet finalized the split.

In fact, court records show in March the divorce case was headed to trial … though it”s unclear what issues were still in dispute. FYI — the couple had 4 children together.

But Mary”s legal problems didn”t end there — on April 30, just two weeks before she died, Mary was served with a lawsuit filed by American Express … though the details surrounding the case are unclear.