Each of the Tendo girls were approached by Kyubi while their mother was dying and all of them wished for her to live.
The wish was granted, and then she died for unrelated reasons later, because magical girls cannot have nice things.
So now they're a cabal of squabbling perpetual early-teens, desperately trying to hide this from their father who is about the only normal thing left in their lives.
When he introduces them to their fiance, not humouring him (even if he's clearly insane) is not on the table.
Ranma is in the unexplored territory of being the normie. Relatively speaking, that is.
The wish was granted, and then she died for unrelated reasons later, because magical girls cannot have nice things.
So now they're a cabal of squabbling perpetual early-teens, desperately trying to hide this from their father who is about the only normal thing left in their lives.
When he introduces them to their fiance, not humouring him (even if he's clearly insane) is not on the table.
Ranma is in the unexplored territory of being the normie. Relatively speaking, that is.