His son Humphry fitzOdo (remember fitz=son)
As far as I am aware, Fitz was also adopted by the English to describe a denotation for the bastard (illegitimate) son of someone in high station...

i.e. Kings, Princes...

oh hang on, better back that up...

In later times, similar forms were coined for members of the English and British royal family, who historically lacked a surname, and particularly for illegitimate children of kings and princes (Fitzroy, son of the king; Fitzjames, son of the king James II of England; and FitzClarence, son of the Duke of Clarence). From this later use, it has been implied that the name indicates illegitimacy, which was not originally the case.
Ah, thats cleared that up then.