The great thing about sibling rivalry is that it ends with age. Sometimes it can start because one sibling, M or F, from an early age desires the love and the body of the other, and because of an over strict religious nut of a parent and a leather strop, hanging on a hook by the door, prohibited that urgent desire for the other's body.
So it is with these siblings, alone in their one roomed shack, who finally admit to each other that they do indeed love each other, and could no longer live without the satisfying love they have finally found! The only thing is she doesn't get pregnant, ah well. Enjoy!