Apparently one Isaac Unknown, dubiously described as Comte de la marche de Valenciennes, is said to have married the daughter and heiress of Raoul comte de Cambrai, murdered in 896. French Wikipedia calls her Berthe. MedLands thinks this daughter and marriage is likely to have been invented to explain how Isaac came to be comte de Cambrai. The title descended through Isaac's son Arnold.
Probably about 955-ish, the Bishop of Cambrai dissolved the marriage of one "comte Amaury... from Hainault", and his wife "daughter of Isaac". It's assumed she was le comte Isaac's daughter and posterity has given her the name Judith. There doesn't seem to be any other trace of this "comte Amaury".
Decades later, the baronial Montfort dynasty was founded by one Amaury (living 1052), who started building the castle at Montfort. Amaury's father is named as William of Hainault in a passing reference written a century later. William is said to have married one dame de Nogent.
Seems like a plausible guess that this William, if real, may have been a son of "comte Amaury" and "Judith", but there's no evidence.
And we've got some duplicates here, but the Raoul in this line seems to have acquired a bogus Carolingian ancestry while losing his real one. He wasn't Raoul II de Gouy, he was a younger son of Baldwin I of Flanders.
