It really isn't that unlikely that you could share some of the same DNA as Robert De Bruys. My mother is a decedent, and can also claim (Descendant) of Knights of the Garter.

To help complicate matters, The Mormons keep detail ancestry documents. While there is no indication that any of my heritage was Mormon, my grandmother sought information in Salt Lake. I asked her about the religion, and none of the names she found were Mormon. They just keep notes, and were apparently very helpful.