Okay, well Dean hasn't met those brothers and sisters. Of course, Dean doesn't want to think that there are consequences to choosing this place as home.

Dean is a very complicated person and so is the facade he puts up for everyone to see. It's obvious that Dean doesn't like that Cas is shooting down his idea. "We'll keep looking, Cas." He says it in that serious, sober tone of voice he has. Dean wants his friend to be as happy here as he is.