I too am a descendant of Henry Coyne. I've spent a fair amount of time trying to verify various aspects of Henry's story as provided by his son William, including his origins on the Isle of Man. I have searched the familysearch.org collection "Isle of Man, Parish Registers, 1598-1950" for Coyne, Quine, Quane, and now (in response to the previous reply) Cayne, Caine, and Cain. Although I can find a Silvester Quine, he is born too early (1727) and I can't find a son Henry. I can find a Henry Quane born in 1775, but his father's name was Henry, not Sylvester. I've looked through the Summary of Wills for various towns on the Isle of Man, searching of a Silvester/Sylvester (since that name seems less common and lets me use the browser to search the page, rather than being forced to read it all). I have found the combination of John, William, Henry and Silvester in the right date range, but the last name of family is entirely wrong and the father is not any derivation of Sylvester. I am currently stuck and must conclude that either (1) the records I'm looking for are either lost or not available online or mis-transcribed, (2) Henry's father was not named Sylvester, (3) Henry's last name was not Coyne or any derivation thereof, i.e. he adopted Coyne upon his arrival in Ireland, or (4) Henry was not from the Isle of Man. I could order the microfilm of the parish records from the local LDS Family History Center and try to rule out transcription error, though that would be a staggering amount of work and is really looking for a needle in a haystack. Another path would be to try to trace Henry back in time from Belfast (my first record for him is in 1805) to County Down. Do you have any records for Henry prior to 1805, perhaps the name of the town he lived in before going to Belfast?
Patricia Crossno