Question: Who is Melisende Of Lusignan's maternal grandfather?
Sentence (from "Isabella I of Jerusalem"): Baldwin IV, who suffered from lepromatous leprosy, had made his nephew (the only son of his sister, Sybilla by her first husband), Baldwin V, his heir and co-ruler, to prevent Sybilla's second husband, Guy of Lusignan, from mounting the throne.
Relevant evidence: No