Wait so Mori can understand his moms???

Yesss he can. It was revealed that he was able to understand both the alien and human language, which was an unprecedented event. I think it has something to do with his time out in the wild, which is also the reason we don’t see mori talking. I think he’s slowly learning how to verbally communicate though!

Kids have high intellectual development, so learning different language is an ease for them.