Sweet Big Brother

So for a while I have been determined to make Cole use the toilet. He just seems way too big for diapers, especially when I know that he knows he is going potty. I've been shamelessly bribing him with pretty much whatever he could want, which was getting Easton more excited than Cole. Easton kept reminding Cole of all the cool things he could get if he could just go once on the toilet, and was very sweet in reminding and encouraging him. The other day Cole was sitting on his little toilet and Easton started getting excited for him. He looked at Cole and said "Hey Cole, is it okay if I can read you a book?" Cole agreed, so Easton grabbed a book, a little step stool, and sat down to read to him.
Even with Easton helping out to try and keep Cole on the toilet for long periods of time, I have since given up. (You'd think I'd remember this from going through it with Easton.) I can force (yes, so mean, I know) him to sit on the toilet for a long time but I cannot make anything happen beyond that. So pretty much I just tortured both of us for a while. He's a big (he would beg to differ on that), smart, wonderful boy and when he wants to use the toilet, I'm sure he will. The other day as he was sitting on the toilet, he said "Mom, can you please put my diaper on?" and I said, "No, you're a big boy, use the toilet like dad and Easton." (Wow, this sure is making me sound awful.) He got the saddest look on his face and said "No, I'm just little. See?" while pointing at himself. So now I'm done with trying to make him do anything and I'm really hoping I didn't go and mess things up for the future, like he may now associate feeling sad and a mean mom with sitting on the toilet. Oops. I may just have to wait much longer but I can only blame myself.