Father of Ferchar macNeill of Barra

Not related in direct male line, they mean (which is all that Y-DNA can show). But from the Orkneys to Galloway Norse and Celt interbred to such an extent that the main determinant of who was what becomes cultural, not genetic. (If you were raised among Celts to think of yourself as a Celt, you were a Celt, e.g. Somerled of the Isles - direct male line Norse; if you were raised among Norse to think of yourself as Norse, you were Norse, e.g. Thorfinn the Black of Orkney, who was known to have had a Celtic mother *and* paternal grandmother.)

So no, it's not as simple as "who's got the Y-DNA?"