The one I'm attracted to...

So I'm F(21) and he is my brother's best friend M(19) yeah I know he is younger but I don't care like I'm age is just a number types. So here's the thing we first started talking and then we began flirting he had a girlfriend at that time but still, we used to. Recently when he broke up after that we came in a situationship kinda open fling type relation and after that he came to our house on diwali and we flirted a little and had a sneaky little kiss. Now, I only told him that I don't want to be in a relationship and don't fall in love with me and the blah blah... kinda shit but I think I'm falling for him, like I'm in love with him, I'm attracted to him very much I get terribly jealous when he talks about some other girl and I get very possessive over him but now I can't confess that I love him cause I was very clear at the start that I'm not looking for a serious relationship and it'll be casual and he's my brother's best friend too and all. We are totally compatible, though I don't say it he's totally my type and we have exchanged a really steamy and passionate time with each other just recently. He is a good guy listens to me and all and he gives me mixed signals too. I seriously don't know what to do any kinda suggestions are appreciated and can it be that he's fallen in love with me too or can he fall in love with me?