My stepdad is a great and nice guy, and I've suspected for a while that he might be autistic. He's very quiet and reserved, rarely shows strong emotion. Chuckles rather than laughter. He's also fixated on certain things and hobbies, and can talk/ramble about them for quite a long time. He likes puzzles and, what have been given to him, legos. Putting together and taking apart things.
Like I said, no hard evidence, but I could see it.
All the damn time. For older generations, getting diagnosed was a taboo. So people who learned to mask well enough were just that person with a lot of hobbies, who struggled to fit in or seemed like they didn't even try to NTs. I'm pretty sure it runs in my family. Though I'm the first to get a diagnosis I think.