Parents biased towards their favourite kid - tell me your experience

Baised one is like heera Thakur who sacrificed everything but didn't get any thing

No one is impartial, partially done by everyone it's an issue when things go beyond a limit.
My parents have preference on me over my sister but that too due to her behaviour which she didn't thinks that her behaviour is bad but she expects same behaviour when she just sit ideal, orders everyone and don't do single things but have same expectations like me who works 10hours and mostly busy. She keep on crying why parents are partial towards her.