enemy has amnesia/younger version of them, found family/enemies->friends/lovers
Send me a fanfiction trope and/or fanfic AU and I'll talk about my opinion(s) on it!
Having clarified this in PMs, since you mean this as part of a storyline trope including all of these tropes...
Frankly, I haven't ever seen anything like this outside of FE13 but I think I could be into it. It's not often I see anything about the enemy character having amnesia and not remembering why they're even an enemy in the first place. There's lots of deliciousness there for whether or not to trust them, and potential for exploration. I think it works best if the "enemy" in this case was an enemy of circumstance outside of everyone's control more than an enemy due to a complete moral difference or something. P:
Also, enemies to friends is always juicy, and in this case, enemies to friends to lovers is also quite delicious. I tend to not like enemies to lovers because writers make it more about sexual attraction bridging the gap (can't relate lmao) but enemies to friends to lovers...I could dig it.
AND OF COURSE FOUND FAMILY IN ANYTHING IS LITERALLY JUST CHEFS KISS MWAH MATERIAL. How to make me love something? Add found family. Easy as.