Boy, why do you act this way?, No, seriously, what's his problem? Options

[IDreamOfWaffles]

Please feel free to move this if it's in the wrong forum! I'm an utter noobie, so yeah..

I'm 13, f 8th grade
boy is 12, m 6th grade
this is long... because the story is long.

Yes'm, I'm a young one, but 'least I'm not on here all 'omg he dose lykes me?!?!' I'm more confused on this one kid's behavior, that's all...
I'm pretty good friends with his sister, I guess (we only just started being friends at the beginning of the year, but it's all going well. I've never been to her house before, though.)

I used to tease him a bit, I've never had a younger sibling to tease so he was a sub, I guess.. anyway, when I sensed he was getting really annoyed, I cut it out and left him alone... but I noticed something...He was looking at me alot. Not ever talking to me, but just.. glancing, looking away, glancing, looking away, whenever he got the chance.

It's been going like this forever, since about November. I never openly looked at him, so it's not like he's looking to see if I'm looking, I just watch out of the corner of my eye coz I dunno what his deal is. My peripheral vision is great according to the doctors, so, I know he can't tell. I once glanced over at his lunch table, and his friend jumped, got his attention, and pointed at me, like his firend was watching for me.

that same friend also talked to me once, saying, "Hey, I know you, you're the one that... *I hear this kids name in the jumble*" but I can't hear any more than that. and the friend won't repeat what he said.

Once he was stuck at our lunch table and I asked, "Hey, why are you over here all alone?" and he kinda ignores that and just points to my good guy friend and mumbles sometinhg, and I hear the word "boyfriend" I think...? O.o

I've seen him point at me and whisper to his friends with a grin, and I just don't get it. It's been like this, just a few glances every once in a while daily, forever.

Recently it'd stopped, but the other day in the hall we were both getting a drink. He started to look at me, but stopped himself and went about his business. and as we were walking back I was passing him and he was staring at me the whole time I passed.

At recess that day, he'd started at me really intesely and openly, which made me a bit flustered for lack of better word--was he really looking at me? and WHY??? he seemed to notice these thoughts and smirked. and whenever I glanced back he was STILL looking and it made me even more 'flustered-for-lack-of-better-word', and this seemed to only amuse him more.

but, then, today at lunch I had to sit near him, like one table away as opposed to the usual 5, and he barely looked at me at all, and when he did his eyes seemed to look really shy and nervous.?

I'm not gonna BITE him!

what's his problem?

I've left him alone, I understand he's not a little sib substitue, so why does he seem like he's waiting for me to attack again?