So sorry you were treated that way!! I have a sort of similar story. I had my genetic testing at the royal adelaide near the end of my treatment and they did find a genetic fault in my family too. Both aunties had breast cancer one even died of it (they were both older than me when they were diagnosed.)
It was still a shock but it did give me a reason why i got the cancer in the first place. When they traced our family tree we discovered it came from my dads side. It wasnt either of the BRCA genes but a less similar genetic fault that is in the Pten gene called cowdens syndrome.
hope it all works out for you xx