We can just hope Konami release a statement about their relation (because they wear handcuffs) in Master Guide.
They already put the official statement about Wynn (being Wynnda's sister and she leaves Gusta tribe). So the statement about other Charmers still possible. Now it's just a matter about our patience.
But, if I could speculate, Dharc probably not a type of character that can easily fall in love. He might be a love-nihilist type character. He could deeply care about Lyna as a friend, but not romantically interested with her.
Calling me Kaze or Kazemachi is as legit as calling me Eria.