I'm masturbating in my room, when you (my brother) walk in and start watching me. I don't notice at first, but when I turn around I am shocked to see you. You tell me that you're feeling horny, and you'd like us to get off together. I cannot believe you just asked me this, I mean you're my brother! Still wanting to get off myself, I reluctantly agree to it as long as you promise to leave me alone after, that it will be a one time thing, and that my panties stay ON. After masturbating with you for a while, I get incredibly turned on, and the panties come off before we cum together