relationship problems

So on friday my boyfriend and i (he's a graduate & im a senior) went to a football game for my school and his brother and his girlfriend (they both are seniors are like me) were there too but we sat away from them. When my boyfriend and i got there, he started looking for them , and when he found them he told me. So u was just watching the game and then i would see him and he would be constantly be looking at them and that bothered me cause i thought he cared more about their relationship than ours. So i told him to stop but he still kept on doing it. Then on Saturday, it was homecoming and his brother and his girlfriend went as well. When we go there he did the same thing and was constantly looking for them and when we were dancing, i had to pull to where i was facing cause he just kept on looking for them. So i really don't know why he was doing that and i asked him what was the reason for doing that and he said he doesn't have one. i just feel like he cares more about them than me bc he didn't pay attention to me most of the time. he was more caught up with his brother and his relationship. so why would he be like that?