Limerence toward my wife's sister
First, let me thank the forum community for all the great discussion here. I've learned so much, and have so much more to learn.
Now on to my issue... a little background first:
My wife and I have been married for 10 years, and dated almost 2 years before this. We've had our rough patches, but overall I feel our relationship is very strong. We've been through a lot together, helped each other through major life events. However, with a few of these hard times, she and I both admitted to nearly giving up.
My wife is rather close-minded. Loving and caring beyond description, but not a very reasonable person. We were both raised very strict Christian (e.g. drinking alcohol is a sin, church music is vocal only... very strict), and while we've both "lost" our faith (I prefer "deconverted") she is having a tough time giving up the arbitrary moral "values" of the doctrine. (E.g. she continues to believe homosexuality is "gross" and immoral, despite my constant attempts to reason with her.)
I, on the other hand, am her opposite in most ways. I can barely read my own handwriting, and can't even draw in stick figures. What I lack in artistic ability I make up for in analytical ability. I'm very independent - she's "needy." She loves/trusts easily; I've been hurt too many times and have learned to love/trust few people.
Anyhow, I've been interested in the concept of polyamory for several years now, and have brought it up a couple times with my wife. She at one point suggested we see other people, but it was obvious she didn't mean it. I made it clear I didn't think she was ready for that and it hasn't been discussed since then.
Despite being very close growing up, my wife and her sister grew apart when my wife and I got married. Over the past few years we've both been spending much more time with her sister. We've developed a strong familial relationship, and I've come to see her as the sister I never had. She's one of the few people I've let in that didn't hurt me. She was one of the few who accepts me for me, rather than what is expected of me. I'm far closer with her than any of my 9 brothers, and even my parents.
Then about two years ago I found myself wanting a deeper relationship with her sister. I also found myself becoming sexually attracted to her. I don't know why exactly, so I just chalked it up to hormones or some other mysterious psychological and/or physiological anomoly. I had myself thoroughly convinced I was over it.
Then a couple weeks ago I found out she was interested in someone I know to be a real dirt bag. This guy has never had a job in his life, lives in his parents' garage, and does little more than smoke pot, drink himself stupid, and play video games. To top it off, he prides himself on taking "trophies." He sleeps with a girl, then takes her panties and hangs them from the rafters above his bed. (He takes them down when he plans on bringing a girl home, to hide his piggishness.)
Despite all the legitimate concerns I had for her future with this tool - broken heart, STDs, etc - the first and most overwhelming feeling I had was jealousy. (It may help you to know she hasn't dated since her last relationship ended badly about a year ago.) It was shocking to me that I felt so betrayed and heartbroken!
The good news is she and I are close enough I could talk to her about the scumbag and she seems to have gotten over her limerence for him. The bad news is there is nobody I know who trust enough to discuss my limerence for my wife's sister.
After talking to her about the scumbag, she told me she would steer clear of him. The feelings of jealousy lingered only for a few days. A week later, I find myself feeling those old feelings again. I feel the same kind of love and sexual attraction to her as I do my wife. Per my upbringing I feel ashamed, but my brain is asking, "what's wrong with loving two people?"
Then I remember reality. Nobody in my family would be accepting. My parents are still coping with finding out (7 years ago) that I'm an atheist. How would they handle this? What would my father-in-law think of me? Not to mention my wife. I would expect no less than it would break her heart and possibly end our relationship. Not to mention how her sister would react if I told her.
I guess what I'm getting at is I could use some advice. Should I be asking, "how do I pursue my feelings toward my wife's sister without jeopardizing my marriage (and my relationship with sister, the entire family, and the vast majority of my friends)?" Or, "how do I stop feeling this way?"
Sorry for the lengthy post. Thanks in advance for the responses.