I have been having inpure thoughts about my sisters husband, should I tell her or just continue to flirt with?

If I were you I would definately not go with B because I'm sure you love your sister very much and this would devestate her. She loves her husband very much and she would eventually forgive you I'm sure. I might not tell her either because this could worry her and she might not talk to you or not talk to you with her husband around because she is afraid about your crush on him. Also, that is a very bad sin to sleep with someone that is married. It's next to sodomy and gay sex. I'm not saying I disrespect gay people or don't think they have the right to do what they want just like how you can have sex with him if you so please. I would not flirt with him either because the feelings for him will continue and he may have feelings for you or be freaked out that his wife's sister has a crush on him. I would concentrate on yourself and then try to find your soulmate or future husband. (not finding your sister's dick) best wishes