Well, Bell as a brand has been bought and sold numerous times. In 1980, Bell was bought out by Riddell, then split into different units, with the helmet side (Bell Helmets) being sold in 1991 to the Italian company Bieffe, and then was re-acquired by Bell Sports in 2002 (which had also purchased Giro helmets in 1996), which itself was bought by Easton into the newly named Easton-Bell Sports in 2006.

So, the same parent company owns both Bell and Giro.