He is said to have come from the family of the Lords of Saint-Omer (in today's northern France), possibly the son of William I, Lord of Saint Omer and Melisende de Piquigny.
Konon ia dilahirkan dalam keluarga Adipati Saint-Omer (sekarang di bagian utara Prancis, kemungkinan putra dari William I, Adipati Saint Omer dan Melisende de Piquigny.