Kinsale, from Kinsale, Ireland. Changed to Kinsaul at the U.S. Border.

My family's name before immigration was Kinsale, from Kinsale. My understanding is what we at one time had a castle, that we donated to monks / the church that was later almost entirely destroyed in a war, but that the ruins are still there. Having a hard time finding any information and if I believe the internet, there's only a few people left in that area with that name. I would really like to know any stories, people, perhaps even which castle my family's story is referring to. Maybe even find a cousin or two. Thanks!