When I first played Fire Emblem: Awakening, I didn’t know Chrom (The game’s main character) had to choose a wife by the end of Chapter 11. If he isn’t married, he’ll marry the opposite gender character he has the highest support with. This is known as “Auto-marriage” around the Fire Emblem fandom and can happen in Fire Emblem: Genealogy of The Holy War where it’s required for that game’s decoy protagonist Siguard.
Now, during my first playthrough, Chrom didn’t support any of the other ladies because I thought that he could marry any girl in the game (with the exception of Lissa.) When he actually only marry Sumia, Sully, Maribelle, Olivia, female Robin (Who was called Laren in my first playthrough) and a random village maiden. So I tried to marry him to Miriel because I thought it would be funny to have the queen of Ylisse be a bookworm who uses too many hard-to-understand scientific words that no one ever uses. But it turns out Chrom can’t marry Miriel for some reason.
So… when it came time for him to marry someone, my character, Laren, had the highest support level with him (C in case if you’re wondering). So… yeah. I originally intended Laren to marry Lon’qu because he’s awesome. But in the end, Chrom just looked at Laren in the shower and probably thought: “Wow she’s hot.”. Star-crossed lovers, silly trope I tell you!
Long story short: I accidently married Chrom on my first playthrough of Fire Emblem: Awakening.
Note- I am NOT a Chrobin shipper. I don’t even like the ship!