Terms And Conditions On Inlaws Moving In

Funny how parents in law use the "we are older and more experienced" card when you question their controlling, and you become the "mannerless" child questioning wisdom of elders

 

Good to hear this about your sister and her MIL.

However MIL's vary.

The more tolerant ones will behave like your sisters MIL.

The less tolerant ones will behave differently, including and up to cutting off links with a "disobedient" son to bare minimum .... chances of this happening are higher if she has other kids to help her in her old age. If the disobedient son is the only one able to help her, then automatically she becomes more tolerant of him becoming a team with his wife, as the MIL has no other option

So while how a DIL and Husband behave is up to them, but they can not control the MIL's reaction, hence why I do not fully agree with your last line in bold

 

My sister's MIL has another son living closely. Intact her elder son is the disobedient one compared to my sisters' husband.
My BILs obedience is one reason for that mother to like & love him the most. Perhaps that's why she chooses to stay with him than the other son.

So the point is, both MIL & DIL need to be reasonable.
If MIL adjust & accommodate a struggling DIL during her initial days, the DIL would go miles to do the same to her ailing MIL during the latter days.
Of course unreasonable people vary and be nasty regardless of any favor. That's a different case.

My own MIL did not turn up to help us when we struggled. She fueled the fire and made our marriage a living hell initially.
We worked hard with the help of my mother and reached to a point where our marriage is near perfect and nothing could break it.

MIL is healthy now. Touchwood.
But who knows, after a decade or so, she might end up very fragile & need assistance.
I am not sure how much i could extend support to this woman. Bcz whenever i think of her, my mind visualize all the horrible encounters that i went through.
You reap what you sow!