"Are your brothers gross too?"
I only have one brother, but I’m lucky—he’s usually not too gross. :) I do also have three sisters, however, and between my total four siblings, I can definitely sympathize with being frustrated by siblings, at least on a more generic level. I’m not sure if you’re asking for specific advice, but as it happens, I actually wrote a blog post several months ago all about having siblings! If you’d like to give that a read, you can find it by clicking here; hopefully some of that article helps you!
That said, if your brothers are bothering you by being “gross”, I’d recommend seeing if you might be able to figure out why they might be doing that. Have you tried asking them to stop? Without knowing your brothers, I obviously can’t know how they would respond to that, but it could potentially be helpful. Unfortunately, it’s true sometimes people do things that they know will bother other people (such as their sister), and if that’s the case, asking them to stop may not help, but it might be worth a go nonetheless. It’s always possible that they don’t really realize what bothers you, in which case communicating about it can be very helpful. :)
While it can be really frustrating when other people act in disgusting ways, ask yourself whether it really harms you. If not, and if politely talking to them about how you feel doesn’t work (you could also try enlisting your parents’ help, although again, without knowing your family, I can’t guarantee how that would work out), your best option at this point might be to try to ignore it to the best of your ability. I’m not sure what type of “grossness” you’re referring to, but sometimes, you may just have to accept that that is how they are, at least for now. When it’s getting on your nerves a lot, I’d recommend trying to focus on something else; read a book, write or draw something, do some homework, listen to music—really, anything that will distract you.
Hope this helps a bit, and good luck with your brothers! :) I don’t know if this is what you were looking for, but if you have any specifics you want to ask about it, feel free to submit another question and/or PM me directly!
On one final note, I don’t know how old your brothers are, but typically as kids get older they become less “gross” or otherwise immature; I know that waiting can seem to take forever, but I can just about promise you that they’ll mature eventually. Until then, hang tight! <3