STRAY CATS FIGHTING HELP!?

there are two black cats about the same size that hang around my house,i think they are sibblings. they are always together, but they are always fighting! they moan and growl and BAM! attack each other. one riped out the fur of the other one, i thought he had a mouse in his mouth, but it was a tuft of fur! i also have a very sweet docile out door cat (she's sorta tame but we cant take her in, dont worry she's spayed) she hangs around our house all day and we feed her 3 times a day and she has a healthy coat and weight. is she in danger of the other cats? also sometimes i go out and brake up the fights, but would they come at me? they are not rabid, they show none of the symptoms, and this has been going on for months. what do i do? i dont want them to get hurt, and they look kinda scrawny, and i cant feed them because, one is always with the other, and when they're together there fighting. so they are too tense to stop and eat.