"I'm sorry but— You can't be with my niece, it's dangerous." J'onn says softly, intertwining their fingers and resting his elbows on the table. Although his look is stoic, he is actually a little irritated that his niece has such a stubborn partner.

J'onn doesn't get upset about anything, or that's what M'gann told you. He is a Martian with great common sense, however, he here knows he cannot accept you as M'gann's official couple.

Besides the fact that he don't trust you, it's also because of M'gann's powers. "M'gann's ability is unstable, you know that," he comments, "It's hard to say but she's a danger." He knows that what he says is harsh, but it is important, for him and for the League, to let you know that.