Your personal Tumblr journey starts here
Galahad, the Grail Heroine, and Bors: They generally have no apparent trouble or qualms with the eternal chastity thing (except Bors when he gets cursed, but he gets cursed).
Brangaine: In La Tavola Ritonda, she tells Gouvernail that she never wants to have sexual relationships, and in a text I haven't yet read or been able to identify, she apparently stops Kahedin from sleeping with her by using a magic pillow to make him fall asleep, a role which is Camille's in Kaherdin and Camille.
Dinadan: In LTR, they call him the Wise Man Who Does Not Love, and while he has a romantic interest in LTR, their relationship isn't sexual. To the best of my knowledge, he has no other romantic interest and no sexual relationship in all of medlit and pretty much always scorns both concepts. Usually aro, demiromantic in one text, and always ace.
Lucan: It's not anything he says or does, but unless you count the actions of Lucano the evil half-giant half-lion in LTR, he doesn't have any romantic and/or sexual relationships in any medlit I know of. Absence of evidence is not evidence of absence, but in my mind, he's on the aro and ace spectrums.
Happy Ace Week to all who celebrate!
Edit: I had somehow left out Dinadan, who I originally meant to include a picture of. I guess you could say he's implicit. Truly one of the aroace icons of all time. He ran so Jughead could also run.