Family roots in Co. Crk, Ireland also in Co. kilkenny

Hello all! Pleased to "meet" you! My Maternal G'mother, Mary Katherine Sheehan Cranney was born May 1887 Ballymacthomas, Cork City, Co. Cork, Ire;and. She was born to John J. Sheehan & Helena FitzGerald, who married Aug 1884. On the cert. the fathers ere both listed as John. John FitzGerald was still alive, a Baker in Cork City. (FitzGerald Bakery anyone? No idea if the 2 facts are related or not?) John Sheehan was already dead by the date of the marriage. He had been a Laborer/Carpenter, he died in the Cork Workhouse sometime in 1882 of Pneumonia. His wife was Mary Maher, no idea of what happened to her? I don't know if she or John had siblings? Or who John's parents were? No more known about the Sheehan line? I'd like to get farther back! John FitzGerald was married to Jane Anne Leonard. Jane died of Dropsy, John FitzGerald (too many Johns, so periodically I'll throw in a surname to try to keep everyone seperate.) moved in w/another of his children, Mary FitzGerald O'Driscoll, wife of Thomas O'Driscoll (would like to know where everyone lived?) Did the O'Driscolls have a family, kids? John FitzGerald died in 1908, of what, when exactly? John FitzGerald & Jane Anne Leonard had my Helena & Mary, I know there was at least one more sibling, Jeremiah J. FitzGerald, who also came to America, he married Mary Jane McCarthy (where, when?) & had kids (names & dates & locations?) were there other siblings, what happened to them? Johm FitzGerald's father's name was also John (so middle names to keep everyone separate?) FitzGerald, his wife was Mary O'Sullivan. Anything anyone could find to add to all of this would b tremebdously appreciated! I'm at my wits end! I've tried approaching people on the City Council, there a Counselors Dr. John Sheehan, a FitzGerald, a Maher, the Sec. to the Council is Karen FitzGerald, but of course she married in, so knows very little, her husband (I think his name was Tony FitzGerald, also works for the city, but he blocked me, even before I could ask anything!) So I don't know what to do, anyone w/Irish research experience could you advise, help? Be well, Jack MacDonald-Hilton