I am researching my Hanrahan ancestors who emigrated from Ireland about 1849 and settled in Waterloo, Seneca Co. and Geneva, Ontario Co., NY. They are Andrew and James Hanrahan.
I noticed this post and am writing since I have some additional info on Hanrahan families in the Rathbone area. Hanrahan was a somewhat unusual name in the central NYS area in the 1800's and 1900's so I looked for all instances of the Hanrahan surname to help my search.
On the copies of the 1900 census you mentioned I see James Hanrahan family following the listing for your Patrick Hanrahan. James has Sara wife, children: Steven, Ann, Hellen, & Edward (brother. Just above the listing for Patrick are William and wife Jennie, with children: John, Edward, Leana.
In the 1880 census for Rathbone are James Hanrahan, age 60, wife, Ellen age 48, and children Ellen, Timothy, Rosanna , Catharine and Thomas. Also, John Hanrahan, age 64, with wife Ellen 50 and children: Kate, William, Henry, Daniel and Edward. Finally, Patrick listed as widowed or divorced with children; Annie, susanna, Frank, Mary J., Thomas, Martin, Michael, Nellie, James and Joseph.
Last is the 1870 census for Rathbone with Patrick age 50 and his wife Ellen age 40 and Mary, Kate, Willie, John, Maggie, James, Patrick.
I also have a marriage registration from the Catholic Church in Stanley, Ontario Co, NY for Henry Hanrahan of Rathbone, son of James and Helen Hanrahan who married Mary Merriman of Rushville, with witness Thomas Hanrahan.
I have no idea if these Hanrahans are linked to mine, but if copies of the info could help you or someone else I would be glad to send them along. I would also be interested in any other info you have on your Hanrahan's origins in Ireland. I believe mine are from County Limerick.