Here is a question for the group.
I've been married for 11 years. My wife is 11 years younger than I am and she has younger siblings. Well over the past year her younger sister (13 years younger than me) has been extremely flirty with me. At our family Christmas party we hang out in pajamas all day. We played twister and when we fell my sister in law bit my dick through the leg of my sweatpants. The rest of the night she was trying to get at me.
So deciding what I should do. There is no particular order to these options but I believe that they are the only options that I have.