I was born 1966, (57 in August,) which makes me Generation X, but I am right at the start of it virtually. I think they start at 1965. DH was born 1965. We are both 100% Gen X, and not a scrap of 'Boomer' in us, even though we are only just out of the Boomer range. We have NOTHING in common with any boomers we know.
I get on better with people younger than me, even up to 30 years younger (like late 20s) than I do people even 5 years older. I like todays' music (as well as 90s, 80s, and 70s.) And like video games, netflix, recent films and film stars (as well as older ones going back to the 1970s.) I book tickets and meals on my smartphone, I have travelled to about 20 different countries, (a few alone,) and I have lived on my own in London, (for 3 years,) and also Paris (for 6 months,) and I feel about 27 in my head.
I struggle to relate to people my own age or a bit older. I get on with them, but seem to find people between 10 to 30 years younger easier to talk to. Probably because I like stuff they like, and am young at heart, and have a young mind and a young soul. I know people only 5-6 years older than me that frankly are quite boring, (to me.) They don't do much with their life, have never been abroad, don't have a smart phone, have never used a computer, and don't have netflix or amazon prime, they very rarely watch films, or listen to music, and have never played a videogame. They seem a generation older than me (like 25 years older,) not 5-6 years.
DD was born 1994, so is at the far end of Millennial but is still a millennial. 100%. She is in no way a Gen Z.
Like a few other posters, I do roll my eyes at some people who think being diverse, accepting people in same sex relationships, being opposed to racism, and nuclear war, and being a vegetarian, is something people born after the mid 1980s invented. I was born in 1966, and a young adult in the 1980s, and all of that ^ was a thing then. Some people do love to believe they invented things though!
As another pp said, Gen X are fucking awesome. 