For anyone who’s both a khala AND a phupho (or mamo AND chacha/taya)…is there really any difference in the relationship between a brother or sister’s kids??? Traditionally speaking or emotionally?
Re: Nieces and Nephews part 2
Well one might think that being an aunt/uncle by blood should bring about greater affection or a stronger bond. For example, you you become a khala/phuppo through blood as opposed to relations formed through marriage (chachi, tayi, mumani, etc). But I’ve learned that even your relos by blood can treat you like crap n can’t always be trusted…so meh. 
Re: Nieces and Nephews part 2
OH...I went back and read your question again. There shouldn't be a difference in treatment toward nephews/neices based on whether they're the children of a brother or a sister.
My mom comes from a huge family. She only has one brother...who took on the role of a father figure...when my nana passed away. Because he's almost like a father figure....the sisters younger than him (my mom, and two other aunts) are more careful about not offending him.....as in I KNOW that if my they had issues with my mamoo's children.....they may vent to others in the family....but I doubt they'd have the courage to discuss with him issues about his own kids. In that regard...there may be more tolerance (as in putting up with stuff).
Re: Nieces and Nephews part 2
cannot say much since havent become khala as yet. but can say first comes first in my case. already love my brother's kid so much, little room is left for the rest.
Re: Nieces and Nephews part 2
I am just a phupo & can be only that but I don’t think I would’ve differed between my brother’s children or my sister’s. The only difference might have been that my sister would’ve allowed me more freely to do anything with the kids while bhabi might be more inclined to handle them their way.
In any case, the love for the kids would be same. They are kids after all - such cutie mutie guploo munchkins! 
Re: Nieces and Nephews part 2
I am mamo and chchu too. itni choti si age main ban giya hon ab kia kar sakta hon. :@:
anyways, I know children are soul/jaan of parents, if one follow this rule will never been in trouble.
I take care of them and time to time take them to hangout, gifting, bday celebration etc.
I also talk about their studies and motivate them by saying good words.
Re: Nieces and Nephews part 2
No difference........... only difference is that sister's kids visit less often than brother's kids........... so lack of frequency means the sister's kid are a little distant.............. although no difference in feelings from my side.