Guillaume III de Mont-Saint-Jean

• 
• Born circa 1210
• Deceased circa 1256, at the approximate age of 45 years

Parents

• Guillaume II de Mont-Saint-Jean ( - aft. 1233), chevalier, seigneur de Mont-Saint-Jean
• Bure des Barres (1175 - aft. 1233)

Family

• Married in 1223, with Marie des Barres (c. 1205 - 1239), dame de La Ferté Alais, issuing
  • Marie Agnès (1235 - 1301)
  • Marie
• Married in 1239, with Marguerite de Bourgogne, issuing
  • Étienne II