Grand Brother is the stepbrother of Grand Son, although he downright hates him. The reason is that once, as a toddler, Grand Son broke Grand Brothers favorite toy. It didn't sound like much of a deal to Grand Dad, but it was a huge deal to Grand Brother. 29 GeeYears later, He killed Grand Son and turned him into Grand Son II. Just like Grand Son and unlike his father, his mother, and his uncle, He is not part of the Fleenstones.