Patrica, Thank you so much for the quick reply. I'm curious as to where you found the marriage record of James Mullagan and Margaret Geary? I have searched the usual places on-line but not found it. Without an occupation for James it's not conclusive.
It's interesting that you mention Aghada. I have been following up on a DNA match that I have to a Sharon Baskerville that provides a possible link to the Mulligans. I started researching from Sharon's family to see if I could find that link. It has led me to a James Mulligan (tick) who died in 1879 (tick) , Ballydonegan, Cork (???), Chief Boatman in charge of Coast Guard Station (tick) age 51. I believe that he married Margaret Leary in 1856 in Aghada which is across the bay from Cobh where Mary and John married. However I cannot locate any birth records of children that this couple may have had so cannot be certain that these are my great great grandparents. As you said; being naval folk they could have moved up and down the coast. Mary's husband John was also in the navy and their first two children were born in Freeport, Barna, Galway. The next two in East Ferry, Midleton, Cork. My grandmother was next in Dunmore, Waterford and her younger sister in Castletownsend, Midleton, Cork. After John retired from the navy they settled in Old Court, Derrygereen, near Skibbereen, Cork.