Mi hermana me atrae sexualmente

Hello, this is something real and I hope you can help me at this moment. A few months ago my sister for some strange reason started to sexually attract me and I don't know what to do, she's 18 and I'm 19, I masturbate when she leaves with her panties and stockings thinking of her and when she's asleep I come on her beautiful feet and leave all my semen in her bed. I can never stay a day without thinking about her ass, one time we were having a pretend fight and I jumped on top of her, it was beautiful how I felt her ass and my penis got erect very quickly, I wanted to take off her pants and start rubbing my penis with her huge ass. Finally, with all this I want you to help me figure out how to propose to her to fuck just once to feel the pleasure of my semen inside her, thinking about doing it anal so there won't be any problems. Our parents and sister are usually outside and we're left alone, I want to feel her ass on my penis. If someone helps or has something to say to me I'm open to private messages and you can also tell me below.