B.F.
You didn't say if you are using any type of toothpaste--if so, it could be that.
My daughter is 2 also. I usually just wet her brush and let her chew on it, (say while I"m changing her for bed) and then I say OK, it's my turn!I make a game of it--can she copy my faces? (mouth open wide, big smile etc) If that is too much right now, I'd just let him chew on a toothbrush and let him see you and the other family members happily brushing. Sooner or later, he'll want to be "big" too! Good luck!