Arthur Pendragon/Relationships

Le Fay Pendragon
Arthur's sister, not much has been shown on their relationship but it is shown that the two get along quite well.

Siegfried
Siegfried views Arthur as his rival both being great swordsman and having the weapons of opposite natures. Arthur, however, doesn't view Siegfried as his rival, constantly searching for a suitable opponent for his Holy King Sword.

Yuuto Kiba
After Yuuto defeats Siegfried and gained all five of his Demon Sword, Arthur sees Yuuto as a worthy opponent for his Holy King Sword and tells Yuuto that he will battle him when Vali battles Issei.