There's no better research and training program offered to teenagers than their sibling's friends. Here, from the comfort your own home you can study and reflect on how the other gender lives: what they talk about, what makes them laugh, what they eat after school and what they look like sleeping in the basement. I credit my Funny Sister for exposing me to hundreds of hours of "female study" via her friend group. In fact, I believe my first dentist and urologist was little Stacy O, an 11 year-old girl from around the way.
And Stacey O. speaks to your issue: when the study of the other gender turns into hands on field-work-- in your case, hooking up with your brother's buddies. Now in some states I believe you being 17 and hooking up with 21 year olds is illegal. I'm not certain, but I will have my research team investigate this. In the mean time, I'll speak to other issues.
Hooking up with his posse likely has a negative impact on your bro and creates an awkwardness between him and his friends. Friends come over expecting cable TV and your Mom's iced tea and instead they get much more: the Family Jewels if you will.
Maybe your brother plays it off like he doesn't care, but I'd imagine he feels a bit embarrassed, and invaded. Is this inevitable with siblings and their friends? Sometimes, but none-the-less, it's cringy to know one of your friends is hitting the sheets with your sister. Imagine the awkward conversations he will have to sit through.
Joe: Dude, you know who gives the best blowjobs?
(Enter your brother into the room)
Joe: Um..., no one. I don't remember.
Now, of course this isn't always the case. Maybe you're hooking up with a really sweet guy who wants to build a long term relationship, but your question speaks to "hook ups" and plural friendS.
My advice: explore and train somewhere else. Otherwise, it'll likely cause a rift between you and your brother; it'll likely isolate your bro from his pals and the biggest negative: it puts you square in Baby Sister Booty Call Land. And that's a place you don't want to call home.