From the book series "Caraval", jacks of hearts is one of the fates. He is not a fate of love, but of hearts, both physically and mentally. His only weakness is his one true love, a girl immune to his kiss that tends to bring most girls hearts to stop. Though just because it's his one true love, doesn't mean he shows it in the same way others would. Afterall he's a fate and to love, would mean to give up his immortality and become mortal.