For this purpose, friend does not include parent, child, aunt, uncle, niece, nephew, grandfather, grandmother, or other relative. Nor does it include people you’ve had sex with. Why? Because if I felt like talking about sex I would have phrased the question that way, that’s why.
Bonus points if you want to tell us why you were friends with someone much older or younger than you.
I’ve got friends that are 10 yrs older and some 10 yrs younger. Not really very many my own age. The 10 yrs older friends were all made through work - but we maintained the friendship after we both left the company.
The younger ones are usually due to meeting them through one of my husband’s friends - their SO’s.
About 50 years. The woman was a former professor of my husband’s. He became friends with her and her husband, and I did as well after hub and I were married. Really cool people, very well-educated, worldly and well-traveled. They both lived very interesting lives (he passed away about 6 or 7 years ago, she’s still here and in her mid-90s).
Around 50 years. Mostly friends I made fishing and hunting.
When I first started college, I became really good friends with one of the professors. We maintained a close friendship after I finished his class and he retired. I was 19 and he was 78. I guess that is an almost 60-year difference.
Law school is an interesting place - plenty of people go in straight out of college, but plenty of others wait a few years, or five, or ten. I went in straight out of college (age 23), but I had plenty of friends who started in their early thirties. I was usually surprised by that, actually - other than the one dude who’d already started losing his hair in a big way, it was rare that I had much of a sense these folks were older than me. This may have been, in part, because we were all doing the same thing - but I really don’t think people change all that much between their early and late twenties.
Good friends, or bar buddies? For bar buddies, something like 30 years. For good friends, as in we go out on the weekends, go to lunch and hang out at each other’s houses, 15 years. My best friends here in Mpls are 11 and 15 years older than I am. It doesn’t feel like there’s an age difference, but I suppose there is.
Only relatives & lovers are disqualified by the OP, though in fact I’d prefer to hear about people who, if they learned you were alone and lonely on thanksgiving, would immediately invite you to come over and share in the turkey.
There’s about a 17-year difference between me and the slightly-more-mature person who facilitated me meeting my lovely girlfriend. I’m fairly certain I’d be warmly welcomed at any holiday gathering, or pretty much any other time she wasn’t busy. I have a coworker friend who is that same age who would treat me the similarly.
I’m not really close to anyone significantly younger than I am that I can think of at the moment.
Counting only people whose numbers I have programmed into my phone, I’m about 35 years younger than my oldest friend and 15 years older than my youngest friend. In both cases, we met through a mutual interest in certain genres of independent music.
I’ve become friends with my best friend’s little sister she’s 7 years younger then me but we get together whenever I’m in town and I chat with her more then with her brother, of course he;s over in Afghanistan so it’s hard to chat. She is also my personal fashion consultant and lately I’ve been going to parties with her as well so I count her as a friend.
On the old end there is a guy on my rugby team who is in his mid 40s, 15-17 years older then me, he’s come out to the bars with us a couple of times and we occasionally text questions about our families but I’m not sure I’d count him as a friends as much as a buddy.
My oldest friend is 60, which puts her 31 years older than me. We met in Everquest, became in game buddies, and eventually met up in real life. Been friends with her almost 7 years now.
40-some years- the lady and her husband are friends of the family, so I guess I sort of inherited them. 
Incredibly fun, well-traveled, worldly people with a great sense of humor.
No more than 10 to 15 years.
I’m very good friends with one of my ex’s mom (the ex can DIAF). She’s 25 years older than me and lives in another state. I visit her every other year or so.
My business partner is 11 years older than me but we are on a similar path life-wise (bought houses around the same time, he had a kid around the same time my similarly-aged friends did) so it doesn’t “stick out” that he’s so much older.
I’m friends with Athena and Mr. Athena, and they’re proper adults. At least 10+ years older. We’re rogue programmers and dog lovers 
I don’t have friends much younger than me. I am very not cool.
My oldest friend was in his eighties; my youngest friend is 6. I’m nearly 43. Love(d) them both dearly.
As I recall you’re significantly older than I am.
My oldest friends are probably Messrs. Waters & Herron, who are the oldest members of my RenFaire guild. They’re each almost old enough to be my granddad.
The person I would be most likely to describe as a friend is a lady over forty years older than me. We worked together for a couple of years before she retired and we still talk occasionally as well as exchange cards and gifts.
Your youngest friend is not 6. Relatives, for the purposes of this thread, don’t count.
How DARE you! Our age difference is within single-digits! You better not even be LOOKING at my lawn!
pulls tennis ball from walker and hires neighborhood kid to throw it at Silver Tyger Girl