Guillaume I De Thiers Vicomte

Guillaume I's father was Guy II De Thiers Vicomte and his mother was Raclinde ().  His paternal grandfather was Etienne I De Thiers Vicomte and his paternal grandmother is Ermengarde ().  He was an only child.  He died about 1048.  He was buried about 1048.

They had a son named Etienne II.