The calculated distance (air line) between Bonn and Braine-l'Alleud is approximately 119 miles respectively 192 kilometers.
By car or train, the actual journey to Braine-l'Alleud is certainly longer, as only the direct route (as the crow flies) between Bonn and Braine-l'Alleud has been calculated here.
Air line (approximately)
192 kilometers
104 nautical miles