P.G.
Keep the pullups so he can pull pants up/down when HE wants to go. Take him to the bathroom with you when you go but don't make him. He should also follow daddy and brother because they're boys.
My son didn't train till he was older than 3, and when he was ready, he did it in less than a month. Find a fun book about it or create a comic strip about it.
My son attended kindercare in the age 2-3 year room. They had a little bathroom and the kids went. The room teacher gave me the process. He had other kids to model after, and she told me when to switch to underwear. There were a few messes, but it was no big deal. It was when he was ready.