Your brothers tears probably only prolonged the inevitable. If they separate, that's better than them resenting each other for the rest of their lives. Aslong as they remain civil it won't be so bad. I know it upsets you that your parents may separate and you will have to choose which one to live with (most likely your mother) but as you get older it will become easier for you. I don't remember my parents together (or my father anymore) but meh! Whatever happens, happens.