You are spot on about the 2 definitions of fairness--it’s the difference between equality and equity. I tend to be on Team Equity when it comes to fairness. And they can do something about the different money needs if big sis isn’t a big controlling dick about it and will only entertain Team Equality because she likes to look like Team Generous, but in reality is Team Control. One can hope.

I love your last paragraph assuming the best intentions from Jack and encouraging the best out of all of them to sit down and communicate. I want to live in the world you describe here.