Potty Training

I just wanted to say how discouraged I am about potty training Gabe. Today I read my sister, Candy's, blog to find that her son Hayden has gone on the potty all day (6 times). Now Hayden is 2 1/2 years old, a whole year younger then my Gabe at 3 1/2 (their birthdays are only a week apart). We've been trying on and off for more then a year now with Gabe. We had very limited success last June for 1/2 a day! Since then every time we try to train him he seems interrested and excited and knows he can be a big boy if he stops wearing diapers, but then comes and tells us everytime he's gone in the diaper or underwear if it's a day we're trying without diapers. I really thought he'd be out of diapers before Caleb was born, but now I've got 2 in diapers which is just not cool! Urggghhh!!! It's been bothering me that he's not trained now for a few months, but now to see his younger cousin doing it before him really makes me think that maybe I just don't know what I'm doing. We've tried pull-ups, they don't work, he just thinks they're a diaper. We've trying just underwear, he doesn't like it when he wets, but he never tells us before he wets that he needs to go to the bathroom. We've tried sitting him on the potty at timed intervals with no success only to have him wet his pants 5 minutes after we take him off. I just want it to be over and have him trained, but I just don't know what to do now. Everything I read on the subject says some take longer then others and their bodies just aren't ready. I've also read that they won't go to kindergarten in diapers, but I'm not so sure about that one! Arrg.