Sadly, my friends from my youth and pre-Marie days have all passed on. And a number from more recently (50+ years) have also passed on.
I would say the longest relationship for me would be probably Marie's and my best friend. Marie knows her from her high school days, early 60's. I have known her from when she started at the same workplace that Marie started at after their post high school business schooling, about 1966. That is where I met Marie also. The friend's husband passed away December, 2020, COVID. So, for me, over 45 years, actually about 56 years.
When our Vince and Natalie were still minors, this couple would have been their legal guardians if Marie and I were gone. This couple and their extended family did and do consider us family, as we do them. We see her and a lot of their family throughout the year (we refer to them as the 'party family') probably a half dozen times a year at various parties. We've seen her and some members of the extended family 4 times in the past 3 months at various parties for one thing or another. And every July, for about 45 years now, all of that extended family (about 30 people now) and my family (Marie, kids and grandkids, 10 of us), get together at a Wisconsin resort for a week.
There are a few friends from my younger years that I have lost touch with over the years that I keep wanting to call (hope numbers on the Net are current/accurate) and keep putting it off. At my age, I have been surprised too often by looking for a past friend on the Net to try and call and instead find an obituary.