His inheritance of the seigneurie d´Alluyes demonstrates that Guillaume [IV] Goët was the senior male representative of the preceding Goët family, but the source which confirms his precise parentage has not yet been identified.
GUILLAUME [IV] Goët (-1169). The primary source which confirms his parentage has not yet been identified. Seigneur de Montmirail. Baron du Perche-Goët. Seigneur d'Alluyes. "Guillaume Goët", on leaving on crusade, confirmed a donation to Gué-de-Launay abbey made by "Bodard de Saint-Michel", with the consent of "sa femme Isabelle et de ses filles Mathilde et Agnes", by charter dated 1168[1288]. Robert of Torigny records the death in 1169 "in itinere Jerusalem" of "Guillermus Goeth"[1289]. m ([1150/55]) as her second husband, ISABELLE de Blois, widow of ROGER Duke of Apulia, daughter of THIBAUT IV Comte de Blois & his wife Mathilde von Sponheim [Carinthia] (1130-13 Aug after 1168). The Chronicle of Alberic de Trois-Fontaines refers to, but does not name, the third of the six daughters of "comes Campanie Theobaldus" as "quedam ducissa in partibus remotis, hanc postea duxit Guilelmus Goez in dyocesi Carnotensi" specifying that her two daughters were "matrem Gaufridi de Dunzei et Agnetam domnam de Monteforti in Cenomania"[1290]. She returned to France after her first husband died. Her second marriage is confirmed by Robert of Torigny which names "Herveus de Juen" as husband of "Guillermus Goeth…primogenitam filiam natam ex una sororem comitis Teobaldi"[1291]. "Guillaume Goët", on leaving on crusade, confirmed a donation to Gué-de-Launay abbey made by "Bodard de Saint-Michel", with the consent of "sa femme Isabelle et de ses filles Mathilde et Agnes", by charter dated 1168[1292]. The necrology of the Prieuré de Fontaines records the death "13 Aug" of "Domina Elisabeth…monacha, ducissa, soror domine Marie ducisse"[1293]. Guillaume [IV] & his wife had two children: