Question: Who is Empress Gao (Former Shu)'s father-in-law?
Sentence (from "Wang Zongyan"): He was the youngest son of Former Shu's first emperor Wang Jian (Emperor Gaozu), but became his heir because his mother Consort Xu was Wang Jian's favorite concubine and was able to gain the support of the chancellor Zhang Ge.
Relevant evidence: Yes