Hi Peter, I don't know if you are still researching the Kerlins but I am one and am working on Ancestry.com. My great grandfather, James Kerlin was born in Tannagh, near Claudy, County Derry in the Sperrin Mts, in 1822. He emmigrated to Pennsylavania in 1842 but left behind four brothers and a sister was born later. My tree is public. You'll find it under KnittingNana or knittingnana (Sheila Kerlin is home person but it's the Prince Tree).
I'm stuck on his parents. I only know that it's James Kerlin and Mary Ann (no maiden name). If we can pin them down to County Derry in the Sperrin Mts. I bet we are related. The first Kerlin ancestor I know left Ireland because of business restrictions in his field of tailoring and went to London. His son became a member of the Royal Guard and was serving in Ireland and he fell in love with an Irish lass, Mary Ann, and so left the Royal Guard, married Mary Ann, and became a farmer. Both are burried in St. Patricks cemetery, Claudy. One of their sons, James, got involved fighting against the Crown and so because his life was in danger, his parents sent him to Philadelphia to some Kerlin cousins (don't know whether they were cousins from Ireland or England). He then ended up in Pleasant Mount, PA. where my grandfather, Thomas, was born.
If I can give you any more help, let me know. If you can't get into my tree, let me know and I can give you the names and birthdates of the Kerlin siblings that James left behind.