Well, I guess it's a case of woman on top, explains the kids.Bai-sa is female, bhai-sa with a ha is male. Still it sounds the same to me, being a South Indian as well. But thankfully I have not asked my guests to sing.
Mohini hates the bhai-sa because her sister ran away. She hates her sister, because she got the handsome sexy thakur sa and became the thakurainsa. Green eyed monster doesn't differentiate between blood and otherwise.