LeX (may I call you LeX?) carries some valid points. There are some things you can't ignore. Somnambulist is a possibility, so is household pets. The only reason I don't tend to question people who say they "know what they saw" is because I have seen a full manifestation, only once, and all the explanations were there. It was dark, I had just woken up that minute, I was young but.... I know what I saw! Even with all those explanations, darkness, sleepiness and a childs imagination can't make a human being magically appear as clear as the nose on my face. People will argue with that but any rational person can tell the difference between an illusion and reality.
OK. Lex it is. You are right. 99.999999999999999999999% of hauntings are BS. Usually explained by easy means. That's just human nature. Something freaky happens the brain produces the scariest situation, or if you already believe in the supernatural some people will automatically jump to it, generally because they have spent time trying to find evidence of the supernatural and now have something that could be. But if someone tells me they saw something, I will always listen to what they have to say. I trust in the person to have enough common sense of there own to have eradicated other possibilities.
One more point I want to make is why I asked where you saw the ghost:If he came from ur brothers room than we can say there actualy was a ghost, I'm unknown for what reasons he was there, perhaps like said before because you changed your wills, but the fact he came from your brothers room through yours and be off again really makes me think he was just passing through.