Last night, I managed to put into words the rules by which this family lives, and here they are:
Rule #1: Don't f*ck with Kathy (i.e. my mother-in-law).
Rule #1a: Or anyone that came out of Kathy.
Rule #1b: Or anyone that came out of someone who came out of Kathy.
Rule #1c: Or anyone that Kathy has taken in or adopted.
Rule #2: Or God help you!
I admit that usually the rules seem a great deal more complex than this, but I have found that they can be broken down to these simple concepts.
And I told Kathy these rules last night. She was pleased.
Addendum:
Technically, the reason the family is in chaos is that they have FAILED to follow these simple rules.