I have two one from growing up who's 3 years older, and one who's a year or so younger (well, 7 months, but a grade in school younger) frm high school.
The first one I met when I was about 9 or so. We hated each other at first, but by the time I was 10 we were really close and terrorized the neighborhood together. So, that woudl be 20 years.
The younger one I met when I was 16, so that's been 14 years ago.
They're very different, but they're each so special to me in their own way.