Sis thought it was funny when I asked her to be my prom date. She didn't think it was funny when I took her to a bedroom at an afterparty. Sorry sis, it's prom tradition!
Sis and I drove together to her best friend's house party. After drinks, and some dancing, opted not to go home. But instead made our way to the large master bedroom. And once there, got undressed and she straddled my bone.