I have potty trained two boys. All I can say is, he isn't ready. Most boys aren't going to be ready until at least 3 years old. I know (from experience) that you can't make a kid potty train before his (her) time. I would let it all go, go back to diapers, for a few months. I would definitely get his own potty. He is not going to be ready to do the "stand up" stance until he is successful at the sit down. And I wouldn't encourage him to. All you will get is a bunch of pee on the toilet, wall and floor. Again, I know this from experience. Not fun. My boys are 18 months apart, so I understand the urge to only have one in diapers. But believe me, it is NOT worth the annoyance and time to have to change sheets in the middle of the night, throw away underwear, leave a place of business because of an accident.