Hot Sister Hides From Anger Dad in Brother's Bed

I was about to take a nap when I heard my Dad yelling at my sister, the next thing I know my sister Melody is busting into my room begging for me to allow her to hide in my room. I guess my Dad found out she was having sex with her BF, I could have lived without knowing my sister was having sex. It is kind of weird to think about my sister having sex but it kinda turns me on, Melody did come into my room only wearing her bra and panties. Melody starts to come on to me, I kinda freeze for a second but my testosterone kicks in and I know this is my chance to fuck my sister. I fuck her so hard and make her moan all while my Dad is in the other room still pissed that she is having sex... only if he knew I was fucking her right now.