There are a few out there that are pleasantly surprising.
I graduated HS with a girl who met her boyfriend / future husband in 8th grade (he attended another school, but wasn't very far away and was also an 8th grader). Shortly after graduation, they got married. To be clear, this was not one of those "she's pregnant, so let's rush to get married" types of things. He began working, and she attended/finished college and began working before any kids would eventually come along.
Whether it was 8th grade and the four years of HS that followed.....or the marriage..... I have never heard any stories of them breaking up and getting back together, or separating, etc.
I don't interact with either of them regularly, so it's certainly possible I could have missed some major news items, but for all intents and purposes....it seems like they may as well have been married since they were 13 and somehow have made it work.