On her birthday she brought her little sister over for her boyfriend to fuck in the ass. It was really a treat for her, she’d only have to suck his cock every few strokes up her sister’s ass, instead of having his cock crammed into her own asshole all night. She was a little worried that he might decide her 18 year old sister had a better, tighter asshole, but he assured her that even if he decided to start fucking her little sister on a regular basis, she’d still be his girlfriend and get to service his cock daily. She was so glad she had such a great boyfriend.