I tie up his girlfriend while i suck his cock and fuck him

I'm a bitch, i admit it. the other day i tied up this guy's girlfriend at home, who is my own sister, and in front of her i ate his cock, made it hard as an oak and the guy didn't want to stop or let go of his girlfriend either, but he let me do everything and soon, when he put his finger in my slit and made me horny too, i climbed on top of his big cock and galloped while the other voyeur stirred in her bonds, furious with jealousy.