That's really hard. Is he worried about the finances? Saving money by living wit the p's can be motivating to some. But I think a couple really meshes most when they create their OWN home without either's family involved. good lcuk
It certainly doesn't sound pleasant. Have you asked him why he wants to be under the same roof as his parents? If he wants to stay near them that is one thing, but the very crowded living conditions can hardly be pleasant even for him.