Possible...?

This guy (we'll call him Alex) is acting really weird around me. For all 3 years of middle school, I hated him and he hated me. Or so I thought. He was always acting really "smart". The kind of person that is really annoyingly smart. He could be nice at times, but I didn't really talk to him much. Once we reached 8th grade, he started being really nice to me, talking to me all the time, staring in my direction in classes. At the 8th grade dance, he asked one of my friends (a guy, if that makes a difference) to find me...Thus, when I passed him, he tried to get me to request a song. Then I passed him again. He pulled me to the side and asked if I was having a good time.
Now, Alex is sort of....not very well liked. He doesn't really like girls, and when his friend was with a girl (in September), he wasn't too...yeah, you know. Happy.
Now, I'm not very comfortable around guys. I once did like someone, but I haven't in about 5 years. Yesterday was the last day of school, so I'll be going into 9th grade at the same high school as Alex. If this information helps at all....
Anyways, I'd like some advice because this is....confusing. Is it possible to like someone after hating them for 3 years?
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By the way, I hope you've realized that Alex is not his real name. I know you have :)