Hi S.. My son is almost 2 1/2 and we have been potty training. I have a small potty that I started using with him. In the begining it took a few times to get him to go at all. We have these little ones in diapers since birth, so my son never even saw himself pee and had no idea what I wanted him to do. :) I have a 5 year old son too, so what we did was when they went to take a bath I actually put them in the bath first and while they were standing i held the potty up to them and first my 5 year old went and then my little guy. He was SO EXCITED the first time he saw himeself pee. It was pretty funny. ha.
Anyway, we've gone on from there. I've left him in regular diapers and just would time it in the beginning and it's just become a habit for him. He still doesn't tell me before he goes. He will tell me RIGHT after, but never before...so far. But he is little and I know it will come in time. But in the meantime at least we're saving money on diapers and making progress.
I live in Russia right now and they have their kids go on the potty from a VERY young age. Some even before a year old. I know these children aren't "TRAINED" really. I think in the states we call it "elimination timing" or something becuase that's really what it is. But it creates a habit in them. I have seen some kids here at like 1 1/2 who are going on the potty and asking to go. Pretty amazing. I wouldn't do it that young cause it's just so much work, but at 3 years old I don't think you're forcing him to potty train, you're just beginning to teach him a new, very important skill.
It says you have 2 boys...is one older? If so maybe your little guy could watch him pee a couple of times and then just try it with him. The bath worked good for me because the water made him want to pee. :)
anyway, good luck. Don't get stressed. It's really a huge milestone for them and it's a big deal for mom as well. Maybe once he starts going at least sometimes during the day you can try getting him to go before bed. Let me know how it works out! :)