Guillaume III De Saint-Omer

Guillaume III was born about 1115.  Guillaume III's father was Guillaume II De Saint-Omer and his mother was Melissende De Picquigny.  His paternal grandparents were Guillaume Ier De Saint-Omer and Aganitrude De Bruges; his maternal grandfather was Arnoul De Picquigny. He had a sister named Mahaud.  He was the older of the two children.  He died about 1170.

They had a son named Guillaume IV.