Is it normal for my brothers best friend to be sending me these signals?

My brother has known his best friend for almost 2 years. At first, me and this guy would occasionally chat, we never really talk and we didn't know each other that much, then their sports season came up a few months later. Since I started seeing this guy more, we would start talking more, just about common things like the sports team and school. He was a junior at the time and I was an 8th grader (I know, pretty big difference, but please don't focus on age as much with this one). Anyway, over the summer, we had the same job, including my brother (we all coached at the same club), and we started getting really close, we would talk a lot when we were together. It wasn't awkward to be the only 2 in the room anymore. We were really good friends. Once summer ended my season started and all the girls on the team were obsessed with this new guy that was my brothers best-friend, which I thought was weird because he was just like an older brother to me now. Since my brother, me, and this guy would spend a lot of time together, people on my team started asking if we were dating and of course I was like "no, no way haha". Girls on my team also started hanging out with him at parties and stuff. Anyway, after the season ended and school was already a few months in, I started developing a few feelings for this guy that I'm always with. He kept acting like a big brother and I always acted like a little sister. Anyway, fast forward the summer again and we started working, we started getting really close. My brother took work off for two weeks because he was out of town, so it was just me and this guy. We would do everything at work together, it was so much fun. This is where I felt like he started liking me, and I started liking him a lot more. We would hang out for hours everyday and just get really close. BTW he does have a girlfriend that he would complain to me about. I was cool with it, like whatever, he's my brothers best friend, I doubted there was any chance. So anyway, fast forwards to after work ended in about August (keep in mind he always comes over to my house). We would all go swimming really late at night. And of course I would let them have there boy time and everything. I would also cook some stuff for them. I then started going to the gym with them. They were both encouraging me to. At this point, he would still talk about the girls and everything. So I'm like, ok he's like an older brother to me, this is cool. I still of course really liked him, but I didn't want to ruin our good friendship. So anyway, this is where I'm very confused. One day, I think the third day I went with them. Me and this guy went up to this deserted room, alone, and my brother was still lifting. He was teaching me some really cool stuff. And let's just say things got very touchy. He would. Take my hand, you know, kinda flirty touch. And I was like, woah... is he into me? I'm confused. Cuz with my brother he acts like an older brother, but when we are all alone he shows off his muscles and he's very flirty. So I called my friend about this, I usually hate drama and stuff, but I needed her help. We talked, and she was saying how he definitely liked me, blah blah blah. I started to get really into this guy. He came over I think the next day, and he would still talk about girls and we may have had a tiny argument on which way to do something. He's a bit of a "I'm always right" kinda guy. Then when we were going to our gym, he was talking bad about my friend and I was saying shut up, and kinda getting mad at him. When we got to the gym, it was raining really, really hard, and he touched my lower back and everything. And then he was just walking around the gym with his shirt off and stuff. But anyway, here's an overview. He talks about girls in front of me, he always smiles at me, we never really text (both of us aren't really texteds), when we are alone he's usually very touchy and flirty, even sometimes occasionally in front of my brother he will sit right by me, he's gotten mad at me for talking with my friend in the car, I got mad at him. So I just don't know with him. Please tell me what you all think.