Is it normal i want to cheat with hin?

Okay. I'm not going to tell you how old I am. But other than that, here's my story.

I have 3 best friends. 1 is in the mental hospital, one knows what I'm about to tell u , and the other Is going to get really Hurt if she finds out

I have a boyfriend. I love him more than anything in the entire world. I wouldn't break up with him for anything. But that all just changed.
My best friend, the one who is about to get really hurt, lets call her Linda. So Linda has this brother, he's a lot older than me and I kind of like worship him. It's like a joke that goes on u know, ? And so like he doesn't (didn't) know I exist and all that I'm just one of his sisters friends. But I mean I smoked pot with him once and ended up telling him I love him and a bunch of shit. But other than that, he barely knew me. So tonight he texted me, And we were talking about other shit (he never usually texts me, it was really weird) and he told me he wants to hook up. I was like spazzing out. This is serious, and he said no one will know and just yeah. Oh, and another thing, linda is madly in love with my boyfriend. So if she found out her brother, let's call him Jon , hooked up with me she would practically murder me. And btw when he says Hook up he means make out. And yeah. I told my other friend, and she Says I shouldnt and yeah I told her I won't. And he later referred to it as "have a thing" .. Idk what that's soposed to mean. And yeah.

So here's the thing, I know its not right. I know I shouldn't, it will fuck up my entire life if anyone finds out. But I mean, I REALLY like him. But like. Nothing more. And he's REALLY hot. This is like a once in a lifetime opportunity, I swear . he's like in a band, dropped out of highscool, and totally bad ass.

But if I do and anyone finds out, then I will lose my friends and my boyfriend. Ik I'm young and this won't matter in my future, but it matters now.

So , should I risk everything I have for what I want? Of do what's right?

So, yes or no? Should I?