FMG Medlands begins their study at Hasculf fitzEudo de Saint-Hilaire-du-Harcouët without identifying a father for him.
https://fmg.ac/Projects/MedLands/enguntps.htm#_Toc112738898
SAINT-HILAIRE
Loyd indicates that this family originated in Saint-Hilaire-du-Harcouët in the present-day French département of Manche, arrondissement Mortain, canton Saint-Hilaire-du-Harcouët[1009].
[Two] brothers, parents not yet identified:
1. ASCULF de Saint-Hilaire (-1121 or after). ["Apud oppidum Santi Hilarii, Harchodio vicecomite, Petro fratre eius" witnessed the undated charter under which "Radulfus Filogerensis et uxor eius Avicia" donated revenue to Sainte-Trinité de Fougères[1010]. It appears likely that "Harchodio vicecomite" was the same person as Asculf de Saint-Hilaire but this is not beyond doubt.] "…Hasculfo de Sancto Jacobo…" witnessed the charter dated to [1100/01] under which Henry I King of England confirmed donations by "Hugo de Grentemesnil" to Saint-Evroul[1011]. “…Hasculfo de Sancto Hylario…" witnessed the charter dated to [1100/04] under which Guillaume Comte de Mortain confirmed donations to Saint-Martin de Marmoutier[1012]. m MATHILDE, daughter of ---. The primary source which confirms her marriage has not yet been identified. Asculf & his wife had four children:
a) EUDES de Saint-Hilaire . The primary source which confirms his parentage has not yet been identified.
b) PHILIPPE de Saint-Hilaire . The primary source which confirms his parentage has not yet been identified.
c) JAMES de Saint-Hilaire (-after 1138). The primary source which confirms his parentage has not yet been identified.
d) PETER de Saint-Hilaire (-after [1157]).
e) --- . m ---. One child:
2. [PIERRE de Saint-Hilaire .
(Power has ALAN as Asculf's brother).
Anyway, I think I'm done with the cleanup.