T.B.
I have a couple of suggestions with a couple of questions. When he naps, what time does he nap? Do not let him sleep past 3:30. Also, what time does he get up in the morning? If you keep these times fairly consistent, he will become a better sleeper. We ended up putting gates on our kids doors when they were getting out of bed constantly. This may be hard since he shares a room with his brother, but it will stop the constant coming to your room. If you don't want to do the gate, there is always the supernanny approach, where you lead him back to his room, the first time saying only its bedtime dear, second time saying only bedtime, and every time thereafter saying nothing, no engaging, no conversation, eye contact etc. Depending on the total number of hours he is sleeping a night, you may want to try moving his bedtime a little earlier. Overtired kids have a hard time falling asleep and staying asleep. When we went through this we moved my son's bedtime up from 8 to 7:30, and he started falling asleep much faster and staying asleep. Most of the time when kids keep getting out of bed it is because they are afraid they are missing out on stuff. Our son is one of those kids, so we try to stay relatively quiet while he falls asleep, then resume a normal noise level. (He falls asleep really fast, usually within minutes of going to bed).
Another approach a friend of mine did was make a pass for her daughter each night, so she has one chance to get out of bed, and that's it. She did this with a three year old, so she was a little older, but it worked for her. The first time she got up she had to hand over her pass, and she wasn't allowed up after that. She could use the pass for whatever she wanted (drink of water, extra hug, anything she can think of). After that one time, she knows she has to stay in bed. It worked for them, but I think it depends on the personality of your child.
As far as getting rid of the nap, I think kids benefit from a daily "rest". At our house, we call it quiet time since my kids don't always nap, but they do have to stay in their room for an hour and be quiet. My son is 4, and very seldom actually sleeps anymore, but I think he benefits from the time to recharge. It was about at your son's age when he started not sleeping every time, but he knows he has to play on his bed for an hour each day. My just two year old has just started to not nap on the occasional day, but she is a real bear come 6:30 or 7:00 on those days, so we have to get her in bed extra early on those days. I know she is no where ready to give up her nap, but if after an hour she is still awake, I let her get up and then move everything else up for the night for her so that she can go to bed early. Good luck. It is frustrating when the one getting you up constantly is the older child. If you have any questions on my post feel free to send a private message. It has been a couple of years since we went through this with my son, but I remember how hard it was not to get a full nights sleep for so long.