From 1207 to 1214, he was held hostage in England in order to guarantee the obligations of his brother Louis II and his wife Ada of Holland to give up the county of Holland.
In 1206, Arnold married Adelaide, daughter of Henry I, Duke of Brabant, and Mathilde of Boulogne.
Arnold and Adelaide had one daughter, Jeanne, Fléron of Loon.
His widow remarried William X of Clermont (1195-1247), Count of Auvergne.
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