Peter of Flanders Dutch priest and politician (1200–1176) Parents Thierry of Lorraine, Count of Flanders Sibylla of Anjou Children Sibylle de Flandre Siblings Philip I, Count of Flanders Matthew of Alsace Laurette of Flanders Margaret I, Countess of Flanders Gertrude of Flanders, Countess of Savoy Baldwin de Flandre Matilda de Flandre Partners Matilda of Burgundy