78-year-old retired housewife fucked in the ass

I believe that love should be clean and neat, as the Bible says we should not do and not like animals that are not aware of God. However, I have not been lucky enough to have people around me who can understand what my spirit seeks. I always have to fall into temptation because I am human and that is what makes me fear the Lord. My older sister always wants it in the ass and I have to give her an anal fuck. Although I would like her to just let me put my cock in her pussy and nothing more. Because I hate having to commit those disgusting sins.