Summary from Wikipedia

As a MacGregor, Rob Roy was a Scottish Episcopalian Protestant by upbringing. [citation needed] He was born in the Kingdom of Scotland at Glengyle, at the head of Loch Katrine, as recorded in the baptismal register of Buchanan, Stirling. His parents were the local Clan MacGregor tacksman, Donald Glas MacGregor, and Margaret Campbell. He was also descended from the Clan MacDonald of Keppoch through his paternal grandmother.[1] Seeing as the name MacGregor was outlawed, Rob Roy sometimes went by his mother's name of Campbell.