A.H.
My kids are the almost the same ages- My son will be 3 in late july, I have a daughter who is 17 months, and my 3rd just turned 2 months.
It sounds like you need to wait it out. I tried potty training several months ago, because I didn't want 3 in diapers. We were at that stage, where he would ask to go occasionally, but he would always go when I asked him to (when i could convince him to try) He completely started refusing to go when I got further along. I think because he was jealous and not getting enough mommy time, since I had other things on my mind. Now that my daughter is here, we've started training again. I started about a month ago, and he's apparently ready now. I just stuck him in real underwear one morning, and said that was it. 10 days later, he was getting up to go pee when he needed to. Now we have poop issues, but thats a whole seperate issue.
I've discovered that this is soooo much easier when you don't have to fight or stress over it.
One of the steps I did, was to use pull ups and not diapers, and make my son responsible for changing himself when he peed. I figured it was a step towards getting him used to pulling underwear up and down, and it also made it easier on me when I was huge and uncomfortable.