My 9yo knows that my brain went a bit wrong (psychosis then deep depression) x 2
He knows my medication is to keep me well. I don't make a big deal of it though he ddoes remember when I was ill and acting strangely.
DS2 is 4.5yo and doesn't really know much.
I will explain more as they get older, mostly because I want them to be in with a chance of recognising MH problems should they develop them themselves
Sadly there seems to be a genetic component