He was the son of Baldwin IV, Count of Hainaut.

In the winter of 1182 on 1183, the Count of Namur-Luxembourg was seriously ill and completely blind, whereupon Baldwin immediately visited him in Luxembourg.

There he was reconfirmed as heir by his uncle and was able to receive the homage of several vassals from him.

The succession was confirmed by Emperor Frederick I Barbarossa on 22 May 1184 at the Diet of Pentecost in Mainz, on which Baldwin acted as imperial sword bearer.

"[2] He was buried at the monastery of Saint Waudru before the altar of Blessed James the apostle.