Casimir II The Just

Casimir II the Just (Polish: Kazimierz II Sprawiedliwy) (1138 – 5 May 1194) was a Lesser Polish Duke at Wiślica during 1166–1173, and at Sandomierz after 1173. He became ruler over the Polish Seniorate Province at Kraków and thereby High Duke of Poland (see Seniorate Province) in 1177; a position he held until his death, interrupted once by his elder brother and predecessor Mieszko III the Old. In 1186 Casimir also inherited the Duchy of Masovia from his nephew Leszek, becoming the progenitor of the Masovian branch of the royal Piast dynasty, great-grandfather of the later Polish king Władysław I the Elbow-high. The honorific title "the Just" wasn't contemporary; it only appeared in the 16th century.

Read more about Casimir II The Just:  Life, Marriage and Issue, Ancestry