I found this easier to understand than Medlands.
The Henry Project: The Ancestors of King Henry II of England: Foulques I "le Reux" (Fulk the Red, Fulco Rufus). (Commentary section) < link > Compiled by Stewart Baldwin
Given the contemporary evidence which shows the gradual rise of Foulques, first without title, then as viscount, finally as count, most scholars have rejected the legendary account of Foulques's ancestors in Gesta Consulum Andegavorum [e.g., Mabille (1871), Werner (1958), Settipani (1997)]. For a recent attempt to find some history in the account of Ingelger and his "ancestors" in Gesta Consulum Andegavorum, see Bachrach (1989) [also, see Settipani (1997) for a response to Bachrach's attempts]. Thus, although Ingelger's name is well documented, nothing certain can be said about him.
The other "ancestors" could be outlined as follows:
Supposed grandfather (probably mythical): Tertullus.
Supposed grandmother (probably mythical): Petronilla, consanguinea of Hugues "the Abbot", d. 886.
Although the "duke of Burgundy" who was supposedly a relative of Petronilla is not explicitly named in Gesta Cons. Andegav. in the passage mentioning Petronilla's supposed marriage to Tertullus, it is clear from context that the person intended is Hugues "the Abbot" (who does not appear to have actually held the title of "duke of Burgundy").