Was So Embarrassed And Humiliated But Ended Up Loving It...

I was at home when my partner at the time made me take all clothes off and tied my hands behind my back and blindfolded me in the bedroom and told me just to  wait quietly until she came back and next thing I felt was someone holding my legs open and licking the tip of my penis and that went on for bout 10mins untill I felt her slowly sitting on me and riding me to the point where I was actually soaked in sweat and came twice and to be honest I never felt so amazing even when she actually pee'd with me still in her but what scared me and still shocked by it even now was when I took blindfold off and seen that it wasn't my partner doin it, it was my sister!! My partner had told her how good I was  and she wanted to see for herself. My partner had been watching and masturbating herself.