robert guiscard
born:
died: 1085
father: tancred d'hauteville [1]
spouse: alberada[1]
child: bohemund of antioch[1]
spouse: sichelgaita[1]
child: roger borsa[1]
i'm just going to jump to deconstructing the narrative. it seems like humphrey I was given the first legitimate fief in the region. guiscard, a norman of noble descent, seems to have taken that fief from him, perhaps with the backing of the church. guiscard was clearly romanized, whereas the other vikings in the narrative may not have been. the church may have consequently preferred guiscard.
william and roger, both said to have been brothers of guiscard, seem to have opposed guiscard's rule. the narrative i'm pulling together seems to be about a group of petty thieves (all of the supposed brothers except guiscard, and perhaps roger) that were protecting their fief from a norman aristocrat that was intent on capturing it. regardless of the precise chaos that went into creating it, the fief was a valuable possession immediately after it was created out of traditionally byzantine lands. taking control of it and protecting it would have been immediate goals of the papacy and it's allies. that a noble should be in control may have been considered 'proper'. in putting down the revolt and restoring the papal fief, guiscard made peace with roger and destroyed william. so, note that, juxtaposed against the earlier story, we also have a story of guiscard subduing a population in revolt. that story of suppressing a revolt is also tied into his second marriage to the daughter of guaimar IV of salerno, as it is said that he attacked william on his request.
in fact, guiscard seems to have been suppressing revolts almost perpetually. malaterra suggests pretty heavy-handedly that he wasn't a very liberal ruler. it seems he was highly unpopular due to his cruelty.
he had to divorce his first wife, alberada of burgundy, herself the daughter of alice of normandy, due to a strengthened papal law against consanguinity by nicholas II in 1058. this may provide a clue as to guiscard's ancestry; it seems to either point towards descent directly from the dukes of normandy or towards a relationship to gunnora, who founded the coutances cathedral. if one suggests that tancred was descended from one of gunnora's parents, it creates a possible consanguinity of level 8 in the roman method, which is fantastical but consistent. a study of alberada's ancestry does indicate that gunnora is the most likely link. this would indicate that guiscard has ancestry in the cotentin near coutances, as malaterra states.
further conquests followed with the aid of geoffrey and roger, leading to the title of duke of apulia as granted by the pope. interestingly, the area that the pope granted robert included sicily, which was slowly conquered entirely by roger. later, he conquered salerno from his brother-in-law, reduced the papal states to temporary vassalage and launched a failed invasion of greece. he supposedly died of illness in 1085.
[1]: the deeds of count roger of calabria & sicily & of duke robert guiscard his brother, books I-III
[2]: consanguinity, inbreeding, and genetic drift in italy (MPB-39), section 2.2