Baldwin V of Flanders

Baldwin V (c. 19 August 1012– 1 September 1067) was Count of Flanders from 1035 until his death. He secured the personal union between the counties of Flanders and Hainaut and maintained close links to the English monarchy, which was overthrown by his son-in-law, William the Conqueror, near the end of his life.

Source: Wikipedia — https://en.wikipedia.org/wiki/Baldwin_V_of_Flanders