Accidentally mating for life - this prompt is killing me!

I need to fill the above prompt for my hc Bingo Card and I am completely blocked on how to fill it.

Any scenarios I come up with involve either ABO (which I kind of hate and don’t want to write) or are pure fantasy AUs (werewolves, magic, etc..) that would involve way too much worldbuilding for me to knock out a less than 4K fill (all I have time for).

I also have the problem that the characters in SGA are older and pretty damn smart. I can’t see them ‘accidentally’ forgetting the rules of their universe and mating for life when they don’t want to.

I’m really struggling for this one. Anyone got any ideas?

Edit: I love melagan! Idea fermenting....