@KatyElphinstone I think one of the biggest problems as a child undiagnosed as neurodivergent, is that it teachs us to take all the blame.
When your way of doing things, seeing the world and interacting with it is never recognised or seen as valid, or even understand in any sort of meaningful way. Then the only feedback we get is negative. The obvious and truly only reasonable conclusion to this is to see yourself as the problem and the one who is broken.
Being brought up in a family with one or more undiagnosed adults can often make this even worse, not better, as many times they can be intent on focusing your behaviour away from what they see as the problematic behaviour that brought them so much pain as children and towards adopting and conforming to much stricter normative behaviours that they see as the solution. In other words the sort of religious masking that worked for them, but of course maybe hopelessly inappropriate for you.
So much of this can be avoided and potentially helped by acknowledging a child's neurodivergence, if only in the general sense and not necessarily in the stricter, having been diagnosed specifically as, sense. Allow the child to realise that difference isn't deficit and the time and space to explore their own particular brand.