That JAV

My sister recently got dumped by her boyfriend and I'm having a hard time with it. She has always been lonely, but now she is taking her unfulfilled desires out on me. She asks me to kiss her and hold her, which frankly makes me uncomfortable. He escalates it further by fingering me and licking my pussy! He even asked me to "just insert it a little bit! and forbidden requests! I refuse, but my dick is so erect that penetration is inevitable. Now, I am doing my best to help my sister with her sexual desires, as if I were in a women-only brothel.