There is a huge difference between someone who is incapable of being sexual and someone who chooses not too, goes elsewhere, is too hung up, who isn't because of relationship issues etc... The example of your spouse being hurt in an accident or being very ill and physically unable make love is a very different scenario.
MJ's reference to fusion is from the work of David Schnarch, "Passionate Marriage". He makes a convincing argument that the lack of sex in many marriages is not a result of a lack of closness but rather that the people are too close (fused) and cannot risk the marriage by asserting their own needs an opinions. In turn, the people become less and less attractive because at least part of our initial attraction to people has to do with their "otherness".
Yes -being a stepparent is tough. Does your H back you up in this role? Does he treat you as an equal parent or as a second fiddle kind of parent? This makes a big difference in how the kids perceive you. My H is my children's stepdad and my 15yo son usually asks him permission to do stuff instead of me. He also asks him for lunch $$, activity $$ and to drive him places. My H has worked hard to get to that point with him. He isn't quite there with DD10 but she still respects his authority.
