The Marquis Odo, who married Emma, daughter of Robert Guiscard.

I can't find a fuller title for this Odo, the father of Tancred, Prince
of Galilee. Does anyone know anything about him? I would like to be
able to name both Tancred's parents, if possible (not just Emma)
without vagueness. Where was he marquis of?

Peter Stewart...

No-one knows, there are only theories. He witnessed a privilege of
Roger Bosso dated 2 August 1099, calling himself "Odo bonus markisius".
It's not certain whether his name was simply Odo, immodestly claiming
for himself the epithet "bonus" (good), or if this was perhaps just
flattery by a scribe, or if he was actually named Odobono.

There isn't even full agreement on the placement of his wife Emma in
the family. She must have been a good deal younger than other known
children of Tancred of Hauteville, but it seems unlikely that she was
his granddaughter rather than daughter as some authorities (including
yours) have interpreted the evidence: she would have to have been
amongst the eldest of Robert Guiscard's children in order to have
given birth to Tancred of Antioch ca 1076, and yet William of Apulia
states that Countess Mafalda of Barcelona, born to Guiscard's second
wife Sikelgaita, was his eldest daughter. He also numbered the children
by Sikelgaita as three sons and five daughters, all of whom are
accounted for leaving no place for Emma as a younger daughter. She
would have to have been the second and born in 1060, and then
overlooked by William of Apulia, or else she would have to have been
illegitimate or a daughter of the first wife Alberada, again overlooked
by William and other historians.

Evelyn Jamison discussed this problem in Some Notes on the 'Anonymi
gesta Francorum', with Special Reference to the Norman Contingent from
South Italy and Sicily in the First Crusade, _Studies in French
Language and Medi=E6val Literature Presented to Professor Mildred K
Pope_ (Manchester, 1939) 183-208, at 195-197.

Peter Stewart