The clones often call each other "brother". They'll usually keep it professional around Obi-Wan and the other Jedi, but they're usually comfortable enough to call their brothers "my brother", etc instead of their names around Anakin.

Sometimes they'll shout "brother" on the battlefield out of habit and then an entire platoon of clones stops what they're doing because they think someone is calling them. It's only happened a few times and even Rex has caught himself doing it.