My slightly younger sister has a intellectual disability/ADHD/ODD. She isn't really NT..in fact, she also has many clear ASD traits and was misdiagnosed PDD as a kid.
She has strong, restricted interests, overall poor social skills, and a high need for structure. Growing up, she was the one my parents focused on and gave all of their attention to because she had so many challenging behaviors. She would fight constantly with our family, and my parents would often get into shouting matches with her. I retreated from this chaotic home life by staying out of everyone's way, becoming quiet/extremely passive and pursuing my own interests. She has calmed down considerably now that she has matured a little and now lives in an amazing group home with excellent staff who truly like her and care about her well-being, instead of taking her behaviours personally.
I love her, but she can a tough kid to deal with as she gets argumentative pretty easily. We have our moments though, and during the brief times she comes home we talk about various things in her life. I have always wanted an NT sibling, just to have a model for what NT behavior should look like and someone to bond with. I didn't have that growing up.
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Given a “tentative” diagnosis as a child as I needed services at school for what was later correctly discovered to be a major anxiety disorder.
This misdiagnosis caused me significant stress, which lessened upon finding out the truth about myself from my current and past long-term therapists - that I am an anxious and highly sensitive person but do not have an autism spectrum disorder.
My diagnoses - social anxiety disorder and obsessive-compulsive disorder.
I’m no longer involved with the ASD world.