I think, canonically, Cynric is "in love" with Anita because she's the most beautiful woman in the universe, and therefore any man (or boy, ick) who has ever touched her (or maybe just seen her) falls in love with her. Any other woman is a poor substitute. Because people fall in love over looks and nothing at all else.

Imo, LKH is setting up for Cynric to either take Nathaniel's place when Nathaniel is killed off for no longer looking 16, or to be drained to death to save Nathaniel, at which point Nathaniel will magically look and act younger again because he has Cynric's life force or whatever.