Frankly speaking it is quite sickening to see parents show preferences among their kids.
I see it with my wife's family. My wife always felt like she was loved less than her siblings. She is second of three kids and apparently when she was young, her older sister and she would talk about how their mom used to prefer their younger sister. On the other hand she and her younger sister would notice how their dad would prefer the older sister. However when my wife feels like she is less loved than her sisters from her parents and mentions it to them, they all deny and accuse her of making things up. It disgusts me to see how they can deny the fact when apparently they would agree on on each one being the favorite of their parents. My wife loves her parents crazily. When we go shopping, she always wants to bring something little for her parents, something her parents always loved for example, a special kid of candy, or a small make up for her mom etc. To me it is quite clear that she is always thinking and caring about her parents more than her sister. But still she gets this shitty treatment. It seems like she suffered for this when she was younger and she continues to suffer from it.
On the other hand, I myself have been on the other side of the problem. My brother would always complain and sometimes even cry saying how he was not loved as much as I was by our parents. This used to hurt me a lot. Even though I used to tell him that it was not true just to change his mind, I would on other side tell my parents how it was not fair for him, and why they keep doing it. Sometimes I would even get really upset at my parents for not seeing and recognizing their actions.
For me this is as issue quite close to heart and I try to feel and understand those who have become victims of such problems.
Some people are not meant to be parents. And not all parents are good. This is one fact we nepalese have hard time admitting.