You come in my room to talk after your first date. You tell me how embarrassed you were that you came so quick having sex for the first time. I tell you that you should practice so you don't cum too quick next time. You ask if I can help, I was a little startled at first, being your big sister and all. You beg me, so I decide I should help. You are my brother after all. I ask you to pull out your cock. Once you do, I begin teasing it, stroking you up and down. I am encouraging as I stroke you, I want you to make it to the end, so you'll be better at controlling your cum. A few times I can tell you are about to cum, so I let go of your cock so you won't. Towards the end, I pull down my top and take off my bra to tease you more. Next time you're having sex, the girl will be naked, so I want to make sure we're practicing correctly. Close to the end, I think you are ready, so I countdown from 15 seconds for you to cum. You cum hard for me when I tell you. I'm so happy I was able to help, and that we could have some quality sibling time