It seems Harrys upbringing was a mix of his mother almost favouring him to make up for him being the spare, then others like the Queen Mother treating him like a spare. There was no consistency so he just grew up confused, to the point he was mid 30s getting angry because a picture of The Queen and the heirs was released and he wasn’t included.It's no wonder Harry's got obvious emotional issues when you think about those things. But I also think that part of Harry's issues stem from the fact that he was initially brought up as 'equal' to his brother, despite their entire position being based on a hierarchy that William was always going to be higher in. I don't think Harry was ever going to be truly happy after realising that wasn't true, because he wasn't prepared for it, and didn't have a plan for his own life other than co-ruling with Willy.
I think Kate and her family are going to be positive for Louis, as is having another sibling who's also not the heir. I also think the distance from Harry is good for him too. There's benefits to being the spare (C+L have the freedom to choose their own lives, where G does not), but those will be difficult to see if he's around someone who's clearly so angry that he was ever in that role.
Harry even mentioned in an interview during Spare promo that William has told him to leave the parenting of his children to him and Kate, but Harry can’t help himself trying to get involved because he likes to fix things and wants to save Charlotte and Louis from his fate. It’s not surprising William doesn’t want Harry in his or his families life right now.