They do not want the parents to know that he fucks his half-sister

Shortly after you have lived together, I started to fuck my half sister. It was his idea, not that I am innocent, but nobody expects that his step-sister to propose sex after two days of living together. But it is what we are doing….. She is more daring than me, is not the matter of our parents. Every time I say that I don’t want our parents to see you, makes me a blowjob. It’s like if I said: “let’s Go fuck”. And I can not resist, she sucks in a very exciting way, swallows always around my cock. And she has this fetish to masturbate using her boobs as they are big in the middle of the blowjob makes me jacking off with her breasts. At this rate I’m sure our parents will find out.