Her Little Sister

I was 15 and having my 2nd real girlfriend to have sex with. One day we were making out in her bedroom, the door opens and her little sister walks in. She wants to watch and practice for her own bf, do you mind?
My gf was 15, her sis 11. It was kinda weird but a turn on to making out while she watched.
My pants got pulled down and then my gf just started telling me how she gave me a bj. Her sis close by to watch. Then suddenly gf moved her head and pushed her sis to my dock and told her what to do. Slowly the sis sucked on my cocktail, being told what to do it got better till I busted into her sister's mouth.
Come into my room this weekend, you can practice more Saud my gf as her sis left the room.
Which was exactly what happened. In the morning the Lil sus would suck me off as my gf watched, gave instructions and fingers her own pushy. I never saw the sis naked, only busted in her mouth a few times till I heard she was active with her bf, then it al stopped.