My wife's younger sister
I am a gentleman in my 40s and married to a wonderful woman for 18 year. My wife and I have known each other for 22 years. We are madly in love with each other. She is my friend, my lover, my mate, my sould mate. I would have it no other way. Wife is same age as me. We are both monogamous and faithful to each other..as well as brutally honest when needed. There are no secrets between us.
In the last year or two, prior to the Covid pandemic, my wife and I have traveled to see her family in Vietnam.. including her younger sister (in her 30s). We have traveled many times to Vietnam prior to this last time in 2019. I never really paid attention until 2020.
I guess the dual events of Covid and the fact my wife's sister recently divorcing her husband, has made me think of her. I am perhaps mildly infatuated with her. I had a sexual fantasy of my wife and her sister in a threesome. It will probably remain a fantasy, and maybe never come to fruition.
My wife knows, and is not necessarily irritated. My wife knows I would never hurt anyone, not would I mess up what I, we, have. My wife knows I love her (not my SIL) In fact my wife jokingly teased me that she could setup something next time we are in Vietnam, if appropriate. My wife teases me about it.
We shall see. I will never say never. Of course, my wife has to agree and be comfortable with anything before proceeding.