"Hi! Um can you rec some Merlin/Arthur age-difference fics, preferably Arthur being the older one but it doesn't really matter. Thank you so much I really appreciate it."
Written as a fill for this kinkme_merlin prompt: Where Arthur is older than Merlin maybe 30/18 and Merlin doesn’t tell Arthur that he’s still a virgin, because he fears that Arthur wouldn’t have had sex with him. But soon Arthur realizes that something is wrong with Merlin with the way the boy is making noises of deep destress when Arthur’s pushing inside of him.
New in town, relationship shy Arthur Pendragon meets Merlin Emrys and gets more than he bargained for. Is he setting himself up for a fall; or will the course of true love run smooth for once? Age difference. Modern AU.
Arthur’s the King of Camelot…nightclub. He can pick and choose who he wants, and he does – often – no promises and absolutely no repeats. The night he chooses Merlin might just be his undoing.
When Arthur finds out that his one-night stand is only 17 years old, he does everything in his power to forget about it. But unfortunately, Merlin has other ideas, and just will not leave him alone.
Arthur remembers first, and to have a secret of his own for once, doesn’t tell Merlin. But that doesn’t mean he can’t have some fun first.
After saving King Arthur’s life, a seventeen year old Merlin is asked to move to Camelot and become his manservant.
When Morgana must go on a three-month business trip, she asks her cousin Arthur Pendragon to ‘keep an eye’ on her sixteen year old adoptive brother, Merlin.
Merlin and company have been reborn over and over, but things aren’t quite the same this time around. Modern!AU
Merlin’s Masters dissertation isn’t going so well and to numb his frustration at being assigned a new tutor, he needs a night out. And then he meets Arthur.
Merlin was just sixteen when he met his best mate’s new stepdad, Arthur Pendragon.
I also found a long fic rec list for age difference Merthur fics here at livejournal.