The primary source which confirms his parentage has not yet been identified. Marchese di Ravenna. [There is] a possible co-identity between Marchese Guglielmo [III] and Marchese Guglielmo/Odo, the father of Tancred Prince of Antioch, nephew on his mother's side of Bohemond of Apulia Prince of Antioch. If this is correct, the first wife of Marchese Guglielmo [III] was Emma, daughter of Robert "Guiscard" Duke of Apulia. Tancred's father enjoyed a sufficiently prominent position in southern Italy to be described only as "the Marquis" in many contemporary records. No suitable southern Italian family of which he may have been a member has been identified. It does appear that the title "marchese" in Italy was at that time limited to families in the north, a logical conclusion considering the original purpose of the "march" being a border area into which a powerful government (in the case of northern Italy, Germany) was pushing its jurisdiction. Tancred's own illustrious marriage to the daughter of Philippe I King of France in 1106 is also best explained if the bridegroom had good family connections on his father's, as well as his mother's, side of the family. The validity of the theory depends, however, on whether any connection can be proved between Marchese Guglielmo [III] and southern Italy. If further information shows that Marchese Guglielmo's activities were confined to the north, it is improbable that the theory would be correct.
The name of Guglielmo´s first wife is not known, other than the speculation noted above. This first marriage is indicated by the absence of Guglielmo´s son Enrico from the charter dated 28 Dec 1101 which names his two other known sons and their mother. 1
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