Who is Jack O'Neill from Luna: A Novel and what is their importance?

Jack O'Neill is Regan and Liam's father. He pressures Liam to be the son he has always wanted. He fears that his children do not idolize him enough, even though he is Liam's hero. Jack also worries that he does not have a proper father-son connection with Liam. When Luna reveals herself to her parents, Jack furiously forbids Liam to leave the house dressed as a girl.