Hello! I really don't have a direct answer for your question. However, what you wrote caught my attention. My grandfather's grandfather emigrated to America in1851. His name was Thomas Horan, and was from Galway. I have found a reference to a baptism of a Thomas Horan in 1831.
It is entirely possible that my great-great grandfather and James Horan were brothers. I do not know the name of my great-great grandfather's father. I would not be surprised if it was Thomas, as the name is very common in my family.
I hope to one day travel to Ireland to research the baptismal records. I'm sure my great-great grandfather had several brothers and sisters - and I would,love to track down their offspring!