Sources

1) Source: The First House of Bellême "William's wife was named Maud, as appears from the foundation-charter of Lonlay; but her parentage is unknown. Du Motey argues that she was an illegitimate child of Richard I ; but I have examined this theory elsewhere and rejected it as untrue. They had six sons : Fulk, Warin, Robert, Yves, William and Benoit." (Data from secondary evidence)
2) Source: The First House of Bellême "William de Bellême was born probably within the years 960-5, although his birth is dated some twenty years earlier by du Motey, who relies on the spurious foundation charter of St. Leonard of Bellême." (Data from secondary evidence)
3) Source: The First House of Bellême "The date of death is uncertain, but it probably occured in 1028. Du Motey assigns it to 1031, which involves a hopeless contradiction in dates" (Data from secondary evidence)
4) Source: The First House of Bellême "For a long time Talvas wandered about, but eventually he took refuge with one of the greatest barons in Normandy, Roger de Montgomery. To him the exile offered the hand of his daughter, with all the lands which he had lost : and Roger, foreseeing the chance of future gain, accepted the bride and received the wandered into his household." (Data from secondary evidence)
5) Source: The First House of Bellême "His wife, Hildeburg, was the daughter of a noble named Arnulf, who has not been identified. By her he had two children, Arnulf and Mabel." (Data from secondary evidence)
6) Source: The First House of Bellême "he confirmed a gift of his brother Yves to St. Aubin of Angers within the years 1060-2. Probably he died soon afterwards." (Data from secondary evidence)