Guermond I, Seigneur de Picquigny

From Medlands:

http://fmg.ac/Projects/MedLands/SCOTLAND.htm#RobertBrusMEuphemia

Daughter of ---. “Robertus de Brus” notified his donation to the hospital of St Peter, York by charter dated to [1150/70], witnessed by “domina Eufemia…”[961]. “Robertus de Bruis et uxor mea Eufemia” donated property to the canons of Gisburne by charter dated to [1160/75][962]. Her origin is indicated by the charter dated to [1150/60] under which “W. comes Albemarle” granted property to “Eufemie nepti mee uxori Roberti de Brus”[963]. Domesday Descendants speculates that she was the daughter of Guillaume´s brother Enguerrand[964], although there seems no reason to choose one of his brothers over any of the others. Another possibility is that she was the daughter of Guillaume´s sister Mathilde, whose husband Guermond de Picquigny is recorded with a sister named Euphemie.

From the above we ascertain that Guermond de Picquigny was possibly married to Mathilde Sister of Guillaume and that Guermond had a sister Euphemie.