My sister's new boyfriend has a huge cock, I want to fuck!

My sister's new boyfriend has a huge cock, I want to fuck him! Fuck, today is the perfect day since she hasn't come home from work yet and he's impatiently waiting, I sneak up on him and start touching his cock, when I see that it's growing so much I don't hesitate to give him a good blowjob and we end up fucking, how many horns does my poor little sister have?