Mullane Family

Hoping for some help with my search brick wall please. I have been searchig for months for a Marriage record for my gr grandfather Andrew Mullane. I have of course found there are a number of men in Cork sharing this name, and my problem is that although I managed to find birth, marriage and death records that fit, plus the birth of my gr grandmother Mary and her siblings, which all fit perfectly, her Marriage Certificate in Brisbane, Australia, definitely says her mother's name is Margaret O'Sullivan, and all the positive matches from the RC baptism, and marriage registers in their parish in Cork name his wife as Margaret McCarthy. (Her sister Ellen would seem to have married a John Buckley, and then their daughter Margaret married a John O'Sulllivan, who emigrated to Australia, and we visited them many times in Parramatta when I was a child. Margaret was always referred to as my mother's "cousin", so that all matches, but I can't seem to resolve this mystery of the different surname for Andrew's wife.) Andrew is listed on the 1911 Census as living in Inchidaly, Clonmeen, Cork, "father-in-law"withJohn Buckley and Ellen and family. I have searched other RC registers in Cork round the relevant dates for all of them. I did wonder if perhaps the first Margaret died, and the second wife was an O'Sullivan, but can't find anything to support this theory either.Any suggestions would be most welcome thank you. Carollyn Potter