Heart Lines (джен)

Everyone is born with a heart line, a pigmented mark running from the heart down the left arm to the palm, which turns color when the person comes of age, telling them when it is time to seek their soulmate. Red indicates a romantic love, while blue is for platonic "heart-friends", as the minstrels called it.
Uther had always told Arthur to ignore his heart line, that it wouldn't matter who his soulmate was; princes did not marry for love, after all. If was lucky, he'd be able to keep her as a mistress, so long as he did not get any children with her. Uther hated magic and would have urged Arthur to ignore the heart line anyway, if he could.
Arthur wasn't sure his soulmate was really a woman despite Uther's assumptions. But Arthur's heart line hadn't even come into its full color yet, which meant he hadn't come of age in the eyes of the gods, despite being named crown prince by Uther. So it really didn't matter: whoever his soulmate was, he wasn't yet ready to meet them.
Then one day his heart line comes in, and it's neither red nor blue.