I told my mum first - I just said "Ds1'ds been diagnosed with Autism and ADHD"
And she said "Oh. Well, I always thought your brother was a bit that way, they say these things run in families. He's bright, he'll be okay."
Because for all my mother's faults, she NEVER questions my judgement on anything to do with my children.
And then I told my brother who said "But I do that, that's perfectly normal!" (To which I responded, "It's not normal, it's weird, and you're weird" - this is a normal way to speak to each other in my family.)
Then I told my sister, and she said "Oh he's like DB then? Except clever and good looking." (DSis was 18 at time)
Then I told my dad, who said "Oh well, this is what happens when children have to sit tests at school, they go odd. I don't understand why he's like that, I can't see that you're doing anything wrong."
And I said "That'#s because he has Autism and ADHD".
And he said "Well, there wasn't any ADHD when I was at school, the cane sorted the naughty ones out."
Then I said "yes dad, or they were caned every day, like your brother Chris, until he left school at eleven and went to live in a motorbike garage at 16 where he was immediately employed due to his habit of fixing them overnight, oh, and nobody in the family has seen him for 17 years because he won't attend any family events, and he still lives in a shed, except that this time it's his shed and he sleeps in a house, and he designs jet skiis and doesn't do ANYTHING else because nothing else interests him ... that sort of naughty child ...?"
Then he said "Oh well, I'm discussing it if you're oging to get upset..."
So I said "......Do you want a cup of tea?"
My mother, brother nd sister follow my lead. they accept that I know basically what I am doing and if I say "don't tickle him" I'm not being over protective, it's because he'll either kick you or vomit. My dad won't discuss it because he thinks he knows best but he knows I won't allow him to make unfounded pronouncements without challenging him.