All good questions. But the first "agreeing to be used only for sex", that is troubling. I think in my case I am looking for more that using someone for sex. I think intimacy, emotional as well as physical, is important to a relationship. Personally, I am upfront about my situation with my wife. I recognize that an intimate relationship can easily evolve into love. Family ... There is often conflict in a family when someone comes in to "replace" someone else. Divorce, death these are a part of life and each person struggles with how to deal with them in their own way. Is one way better than another? Sometimes we react in ways that seem very strange to others.