My (almost 5yrs old) DS has asd, we've been told we wont get an official dx until DS is 11, but have been told unofficially by the health professionals involves that he has asd and it is pretty obvious that he has asd too. His uncle also has autism.
DS is very bright and asked if he had autism like his uncle as he was different like him so I didn't lie to him, was honest and explained everything and got some books which explained autism at a Childs level and DS seemed to understand this and was ok with it after asking a lot of questions.
DS hates the Hoover or similar loud noises so I bought special noise cancelling headphones which DS was very happy about. He visited his dads/grandparents at the weekend as we're separated, and DS asked his gran if he could have a pair of headphones for when he was with them too as he didn't like their hairdryer etc, his dad and gran then told him I was wrong and he didn't have autism.
They mentioned nothing about this to me but when DS came home he was very upset and confused and asked me again if he had autism.
I don't know how to handle this tbh, they undermine me all the time but never anything like this.