I've been told that the original Braynen/Brennan/Brennen came from Scotland by way of the USA in the late 1700's. I have copies of the wills of the first Brennen (who married one of his freed slaves and had 2 sons,Henry and John) and of Henry Brennen. John died at a fairly young age. Henry got married and had 3 children.
My husband's father's family is actually descended from a slave of his who took his name. We learned this after I had done quite a bit of research on James Brennen.