According to the law in your country, incest is illegal.
As I've said many times, the law gets broken all the time, and incest is no different. You are a grown-up woman, and therefore, you are old enough to make up your own mind about what's right and wrong according to your own feelings. I'm not about to preach any view of morality upon you. If you enjoy having sex with your brother, and you haven't been coerced into it, or coerced him into it, then what you do is no one else's business but those you choose to involve.
Having sex with your brother's friends as well, this is another thing. Do you realise the potential for blackmail with such activities? There may come a time when you want to move away from these activities, but the threat of exposure, and a possible prison sentence, is a strong incentive against breaking the status quo. You are also in a very vulnerable position for further exploitation if any of these guys decides to do something that goes against what you actually want., I know from personal experience what can happen when you get yourself into a vulnerable position with the wrong type of person. But this is nothing to do with me, this is you.
You can continue doing whatever you like, and whatever gives you pleasure, for as long as you want, and as frequently as you want; but only if you know you can implicitly trust the guys you're doing this with. Maybe you actually get a thrill from being the centre of attention. It may also be a sexual turn on to you to be used by a group of men. It's not an uncommon fantasy with many of us.And of course, your question may actually be just a fantasy. I'm treating it seriously though, as the things we want to do in our fantasies, can often come to life if we have the courage to do so. You sound as if you are thoroughly enjoying all the things you're doing, so if you love it, continue to enjoy it.
I really really hope that you are taking proper precautions against pregnancy and sexually transmitted infections. Apart from any other consideration, that should be the 1st thing on your mind. It would be an absolute disaster in your circumstances to get pregnant; and if a single one of your partners as an STI, so will all the others in very short time. Make sure your using contraceptives, and make sure you are all in good sexual health. Anything else would be madness.
You are only young male, and glass doesn't seem to figure in the equation. This won't be the case forever, and that's where the problems will come. All the time that you're enjoying yourself, but not forming a lasting relationship, everything is fine; but what happens if you fall in love?
He really didn't give us a whole lot of information with your question, and I think I could give you a better answer if I knew more about the situation. I'm happy to discuss this with you at length if you want to PM me.