I instruct in my own dojo, my wife is one of my students, we have a romantic relationship, we are both over 40 years old. Should my wife stop training or should I stop instructing?
I don't think everythings quite that simple.
I honestly believe that if she started as your student before you were romantically involved, it would have been healthier, as a general rule, to have either stopped the teacher/student relationship first or not pursued the romantic relationship. I should have clarified that I was not referring to existing relationships.
Of course it's a generalization, and I'm sure there have been a lot of successful, long-term relationships that have arisen from exactly the same situation. It's just my opinion that, again, in general, it's not a good scenario for developing a healthy relationship. And you're absolutely correct, it's definitely not a simple issue.
This is totally aside, but I admire the fact that your relationship is strong enough to accommodate the teacher/student role within your marriage. I'm afraid to show my wife how to do something on the computer, let alone actually *teach* her something...