Mother + Uncle's Relationship *spoiler*
Does anyone wonder if Ned did the same thing to Joshua's mother when they were little?
Joshua and Ned already resemble each other a lot, and in the end, Joshua says he loves his sister (which I believe, as he has no reason to hurt her anymore). I wonder if this also explains the mother's weird/nervous behaviour. Maybe she wouldn't remember it, but is still affected by it...
... and it could explain why we never see the maternal grandparents.