“From now on, I’ll act as your father. I’ll protect you, no matter what happens.”
SO I HAD A THOUGHT AND IM GIVING IT TO YOU BECAUSE YOURE THE BEST!!! So any soulmate au where once the youngest one turns 18 you find out who the other is OK SO the day before his, Enjolras decides he doesn't want his life dictated by pre-determined rules, so he impulsively marries his boyfriend, Grantaire. As soon as they wake up the next morning, they see that [enter whatever soulmate au: tattoos, quotes, whatever] matches.