[4] In 1214 he fought alongside King Philip Augustus at the Battle of Bouvines.

[5] His first marriage with Mahaut of Burgundy (1150–1192) in 1178 ended with separation in 1181 and produced no children.

The excuse for the annulment was consanguinity: Mahaut and Robert were both great-great-grandchildren of William I, Count of Burgundy and his wife Etiennette, and they were both Capetian descendants of Robert II of France.

[6] His second marriage to Yolande de Coucy (1164–1222), the daughter of Ralph I, Lord of Coucy and Agnès de Hainaut,[7] produced several children:[8] Count Robert's tomb bore the following inscription, in Medieval Latin hexameters with internal rhyme: Of which the translation is: "Born from the race of kings, and a devoted guardian of the laws, Robert, Count of Braine, here rests covered, and lies buried by the remains of his mother Agnes."

die innocentum, that is, "In the Year of Grace 1218, on the Feast of the Holy Innocents."