Not quite marriage, but back when my best friend and I were about to start college at different schools (both 18), she said she didn't want to do the distance and she wanted a fresh start before college (her response to me saying we should just date).

She comes back from her freshman orientation canoe trip 2 weeks later (she went to an environmental school) and said "f it I missed you lets date". We are happily engaged now 6 years later :)

EDIT: to add to the sappy romance of it, we were long distance for a few years, seeing each other only in the summer and then maybe once a month for a weekend.

I proposed to her the second I saw her when I no longer needed to live separated from her.

I made sort of this deal. My friend from high school, we were always good friends, never dated. I went in the army, she stayed at home. She was dating the same guy the last year of high school and all the time I was gone, he was one of my best friends from grade school. The Christmas before I got out after 4 years in, I was on leave at home, I was hanging out with both of them. I put him on the spot and asked why he hadn't proposed yet. He was evasive. I told her, in front of him, if, in one year, he didn't marry her, I would. They broke up a couple months later, I didn't know that they were fading when I made that statement. Long story short, a little over a year later, we were walking down the isle. That was 2 kids and 26 years ago. Through a ton of stuff, we're still together, we are, above all, still best friends. That friendship has gotten us through distance, death, war, (my) PTSD and depression. I challenge anyone to go through what we have. I wish everyone could find find the love that we have, the world would be a better place.

When I was around 9 my best friend promised that he would marry me when we grew up, if I wanted that, so long as he didn't marry one of the millions of girls, that he said would want to marry him in the future.

We fell in love when were 17, he didn't have anywhere near a million girls wanting to marry him, and now we're engaged. He's keeping his promise, but neither of us settled for each other. We love each other.