J.K.
My son wasn't interested at all until he was around 3 1/2, and no amount of traditional bribery, sticker charts, etc., would get him interested.
We put him in pullups because he saw Dora pullups and wanted them -- I explained unless he was willing to pee in the potty or little potty, no pullups. Next day, we were in the bathroom. Small bribery...
For #2, it was all about fear and withholding a few weeks in, but I completely pulled back and put him back in pullups all day versus underwear during the day, gave him a little laxative (Fletcher's) and we started being "regular" again (no pain, big gain). Then, I went to "you go poo in your pullup in the bathroom" and went through routine of changing and flushing poo together in that room. Then a few weeks later, he was interested in sitting on his little potty a few times, and then he was suddenly OK with poo in the potty.
I'm sure you're consistently doing all the "traditionals" -- taking him with you and Dad when either of you go, getting the little potty as well as a training seat for toilet that fits his body and stepstool so he can do alone, talking to him about "big kids", getting the cool video or book from library, maybe you know older kids he could "go" with, many little steps over several months.
In the end, he is in control of his body, and you're in charge of finding out what will make him interested -- every kid's "switch" is quite unique:)