Question: Which cousin of Joan of Lancaster's father was deposed with her father's help?
Sentence (from "Henry, 3rd Earl of Lancaster"): Henry, 3rd Earl of Leicester and Lancaster (c. 1281 – 22 September 1345) was a grandson of King Henry III (1216–1272) of England and was one of the principals behind the deposition of King Edward II (1307–1327), his first cousin.
Relevant evidence: Yes