My grandfather, Michael O'Hagan was the youngest of several sons of Patrick O'Hagan of county Tyrone (on the border with Armagh). My great-grandfather Patrick lost his estate to the English invaders, and he sent his sons out of Ireland. Some of the sons went to USA. My grandfather, being only 12 at the time, went to Scotland. I'm wondering if my grandfather is one of the brothers of the Patrick O'Hagan you are looking for?
It would be interesting to know more about your O'Hagan