Chewie is basically their second dad, watching the boys when Han gets arrested or is in hiding, and Leia is off doing freedom fighter stuff. He's better at disciplining them too, because he can do the sad growl thing that tells them just how DISAPPOINTED he is.
Maybe he teaches them how to make their own Bowcasters, as is Wookie tradition, and sees Hux's affinity for designing weapons. They bond over debating power vs range, what materials work best, etc.