Envying My Sister

I live at home with our single mom and sister. My boyfriend is always super busy and our sex life is kinda vanilla. I guess it’s cause he’s younger than me and we started dating in college. When I’m home, after 11pm I can hear my sister getting plowed by her bf religiously. My mom is usually out cold and never seems to notice. My sister is so pretty, she’s younger than me and my bf but her bf is older. She’s taller than me at 5’4 but is built like a woman. Her body is to die her, thin waste fat ass, c cups, a cute face brunette. Idk how my mom thinks that is okay because he’s much older than all of us. Well, actually I do because he’s a total stud. Bad boy type with a nice sports car tattoos on his big arms. I’m slightly shorter with a similar body but b cup tits. Long story short I confronted him one day when he came to see my sister but she wasn’t out of school yet so I let him in and offered him to wait for her on the couch. I told him how i thought it was annoying that he’s always having sex with her when I’m trying to fall asleep. I was so nervous and started to get super wet when I saw him blush and giggle. Idk how or why but next thing I know I’m stroking his cock on the couch and pleading him to fuck me brutally. He bent me over the couch and stuffed my brains out. We came about twice when I started to freak out and went to my room and locked it. The morning after was a disaster, I confessed to my sister and we both had a falling out but she never threatened to tell my bf. We made up recently after she forgave me and told me that her bf confessed around the same time I did. Guess we were both feeling terrible. She broke up with him but then got back together with him and now we share him whenever he’s over. When my mom falls asleep I’ll join them. We almost have been caught a few times because my moms schedule changed but we make it work.