He didn't, but she is part of the same family.
So? That's an absolutely awful metric.
And the business enquiry is to my mind "Suspicious"
On what basis? You don't have anything to suggest this that is valid. She has brothers that are apparently arse holes. That's it.
I DO subscribe to Blood being thicker than water so in the OP's position I would regard the Sister as being just as dangerous as the Brothers.
Okay, but that doesn't mean it's true. You don't have any basis for thinking that she's "just as dangerous".
If you want to put everything into the open and make it part of some sort of peace treaty that "might" be a plan (possibly even a good one)
Peace treaty? The OP and the sister haven't done anything...
It isn't sensible for him to adopt this odd family feud.
But I am sure that they know exactly who you (OP ) are!
Work on that basis! :/
How can you not see that you're making assumptions, then stating that you're sure of the things you've said?
So what you are essentially saying is that if someone does something awful, then you automatically distrust that person's whole family because "blood is thicker than water".
Also, to note, "blood is thicker than water" doesn't mean everyone in a family acts the same way, or is the same way inclined.