For your third cousin twice removed
You really don’t understand how you’re related to this guy, but for whatever reason he’s always at grandma’s house on Christmas. Since you can’t figure out the family tree it’s unlikely you’ll find a sweater he’ll like, so make him happy with a Merry Millionaire instant ticket—and maybe one of those ancestry kits to try to figure out if you're actually related. At the very least, he’ll learn your name for next Christmas.