Can someone help me fill in the blanks here as I'm only starting out on my mothers side of the tree

G.Mother-- Margaret Keeffe or O'Keeffe married Joseph McCullagh -- Kilkenny
G.Gran Mother _ Mary Coogan (Gowran 1874) married ? Keeffe or O'Keeffe _ kilkenny -- 3 Children
G.G.Grand Mother _ Margaret Burtchaell married Patrick Coogan -- 4 Child
1. Cant find a record of Margaret and Patrick's marriage
2. Could this Margaret be the daughter of Archdall Burtchaell as I cant find any Information on her.
3. Which (O') Keeffe did Mary Coogan marry and what happened to him as he's not on the census.
Any bit of information would help.