Guillaume comté de Bellêsme et Alençon

  Noted events in his life were:

• Background Information. ⁷¹⁹
William succeeded his father in the seigneury of Bellêsme, to which he added the county of Perche. He was given the castle of Alençon by Duke Richard II. He may have been given Domfront since he built a castle of that name. About 1025, he founded the abbey of Lonlai in the forest near Domfront. This William was supposidly unprincipled and envious. He died about 1028. He and his wife Mathilde had the following children:
Foulques, who was killed in combat near Blavon.
Warin or Guerin, Seigneur de Domfort.
Yves, Bishop of Sées
William, who eventually succeeded his brother Robert

~A Genealogical History of the Family of Montgomery, pgs. 21-22

• Web Reference: William of Bellême.
William was the son of Yves de Bellême and his wife Godeheut. William married Mathilde of Condé-sur-Noireau, William and Mathilde had six sons:

Fulk, died in his father's lifetime.

Warin, died in 1026 under mysterious circumstances. He married Melisende, Vscountess of Chateaudun; their daughter Adela married Rotrou, Count of Mortagne (whose grandson was Rotrou 'the Great', Count of Perche and Morgagne).

Robert, succeeded his father as Seigneur de Bellême, murdered in prison.

Ives, Seigneur de Bellême and Bishop of Sées, succeeded his brother Robert, died 1070.

William I Talvas held the honor of Bellême in right of his brother Ives.

Benoit, a monk at Fleury Abbey

• Web Reference: Charles Cawley's Medieval Lands, Guillaume] de Bellême.
"Ivo" founded Notre-Dame de Bellême, for the souls of himself "conjugisque mee Godehildis, sive filiis meis vel genitoribus meis", by undated charter, confirmed after his death by "Willelmus et Godehildis mater mea" [Marmoutier-Perche, 1, p. 1].

Guillaume married Mathilde dame de Condé-sur-Noireau. (Mathilde dame de Condé-sur-Noireau was born about 944 and died about 1024.)