My uncle seems autistic to me, but nobody else in my family even suspected that. My aunt, a very emotional, nervous, affection-needing person was really unhappy in their marriage, seeing him as a very cold, rude, inconsiderate person, who liked to just randomly wander off during conversations, lock in his room and react with anger when disturbed. He was never comforting or genuinely warm - she said and at times she was thinking he might be just a narcissistic, selfish man she was unlucky to marry.
When she described him I thought - wow, I'd never call him uncaring...
I enjoyed talking to him as he's always been asking very specific questions, with answers that could be one single number or we just talked about interesting topics (particle physicist). There was just that nice space around him, that made me feel not pressured to behave in a certain way, just kind of co-exist close without much talk. Then I tried to spot autistic behaviours in him and it all clicked, so I told my aunt to maybe read a few books about Asperger's and see if anything rings a bell.
Last time I saw her, she said I saved their marriage I don't think my uncle would even like to be diagnosed, but she sees him in a different light now, it's not like he's punishing her with silence or no interaction or affection.