I'd like to offer a different opinion on this--hopefully you will not take offense.

First, I may be like you in that I never curse and it does make me cringe when I hear someone cursing quite a bit (though the occasional swear doesn't bother me too much).
My husband grew up where his version of 'shoot' was just what they said. In his mind, it's no different whether the word is a swear or the word 'fudge,' for example. From your description, it does sound like your brothers have taken things to another level, though.

Having said that, my first reaction to your post was that you were being extremely judgemental and that you consider yourself much better than your brothers. Even though I don't know you or your brothers, I was offended. Why? Well, I've been in many situations with people from all over the world. It is so easy to develop prejudices against people based on how they talk. Yes, I know this is different than cursing, but when I hear someone cursing a lot, I wonder what sort of background they must have come from--it's not fair of me to think this way.

So, my advice, if you want it? Accept your brothers for who they are. They obviously like to try to bother you, so don't let them. If you spend more time laughing with them then trying to note every swear word they use, it will be easier to ignore the actual words they use. Love them for who they are. Joke with them using your own words.

Of course, if you don't like your brothers, the easier solution is to not spend time with them. I don't know if this is the case.

Sorry if this is a bit negative, but I thought another opinion might be valuable.