Sullinger is considered by some to be a German surname. A Sullenger family appeared in Caroline Co., VA in the early 1700s (possibly earlier) and had a tradition of being descended from the St. Leger family.

I think it would make sense for Sullingers descended from the German family, as well as Sullingers with roots going back to Caroline Co., VA, as well as members of the English St. Leger family to be tested.

This would provide a tool for modern Sullingers to determine which of these families they descend from.