As with all of Robert’s Rules, a moment’s consideration demonstrates the Rule's veracity. You will immediately see that it applies to most couples you know. She’s happy with him? He puts up with her? They live like that?
But even beyond those examples where application of the Rule seems self-evident, the fact is that all those couples you think are exceptions to this Rule are not exceptions at all. It’s just that the Rule applies to them with such force, and your misapprehension of their relationship is so complete, that you simply don’t know what you don’t know.
Here? Imagine a happy mash up of “I Love Lucy” (with the ethnicities inverted) and “My Big Fat Greek Wedding” (with pork standing in for lamb), with Paul of Tarsus as screenwriter.