@tomtom78 Based on Chapter 3, it looks like he lives with his grandmother. He'd probably feel like he'd have to tell grandma the full circumstances if he was going to try to persuade her to let Mogu stay.
Given the levels of trust Grandma appears to have in him in this chapter ("Yes, the girl you brought home can sleep in your room."), he probably doesn't want to do anything to jeopardize that.