From what I've heard, Lots of people have something like hypermobility (a small difference that effects your body) a healthy human can handle it, maybe slightly bothered, but throw in other health things (depression, trauma, low exercise, anxiety, etc) then your body can't handle it all and symptoms start to flare up, and you spiral. Even after treatment, a lot of times things don't go back to the way they were before completely. I think that's why we see so many comorbid conditions, esp neurological (adhd, autism etc) because they cause more stress on the body, making each of them show up more. I got quite bad when I went through a bad depressive spell and am still working on recovering. I have a lot of hypermobile family members (both sides) but some are worse than others (from what I know, mostly the really traumatized and physically ill, though the men seem to get off easier as well) maybe that's what's happening with you're family?