Thanks for the advice, ladies! I am ready to put him in training pants full time and deal with cleaning up the accidents but I just don't want to have to be cleaning up the carpet, furniture, etc. Throwing him in the tub and washing his clothes are one thing, but with two boys I've already got enough spots on the carpet and furniture. That's why I'm looking for something that is plastic on the outside.
Initially he was interested in going into the bathroom with his brother, but now he realizes that this is just a ploy to get him to do the same. They are six years apart so I think maybe he is perfectly comfortable being "the baby" and doesn't really aspire to be like his brother. I do agree that they have to be "ready" and you can't force them. I have tried everything; sticker sheets, rewards, timer going off every 30 minutes for "potty time," Bear in the Big Blue House Potty Video, regular underwear, even letting him run around naked all day (and by the way, he is 100% "potty-trained" when naked, as he is too smart to soil the floor, but thinks nothing of going in his pants. I'd continue with the "naked experiment," but it was a little disturbing watching him "explore" himself all day long

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Right now he gets very belligerant when I try to make him sit on the potty. I'd pretty much have to tie him to it if I wanted him to stay there long enough to do anything, so I'm not going to force the issue. But I do want to start using the training pants just to make him a little more "uncomfortable" so that he will at least start telling me AFTER he's had an accident instead of sitting around in it until I notice!