The second clue was his death certificate. It named his birthplace as County Kerry, and his parents as John Gunn and Margaret Browne, the very same parents listed in Mary's marriage record. Mary's name also appeared on the death certificate as the informant. Taken together I concluded they were almost certainly siblings. Clue three was finding George's name on the passenger list of a ship arriving in America in 1890, his address -- Listowel, now the partial word Listo on his stone made sense. Listowel is a town, but also a parish so I knew the family's home wasn't necessarily in the town of Listowel.
The breakthrough came from the Irish Genealogy site. There I found the baptismal records of not just George Gunn, but his sister Mary, brother Francis and a previously unknown sister Seragh. The information included names of parents and godparents, and more remarkably, those transcriptions contained a townland, Ballygologue, County Kerry! The site has records from Roman Catholic parishes in Kerry, Dublin and Cork. Church of Ireland records are available from Carlow and Kerry along with Presbyterian records from Dublin. The site is easy to navigate, and although there are as yet no images of my records, they promise they are coming, along with new records. If only there were more sites like this one, and did I mention, it’s free!