Why favoritism exist even in your own family?

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we are six siblings in the family, and i am the fifth child. I always bothered by favoritism system.Instead of asking why my parents do that, i instead keeping sentiments from my parents. I rather don't talk and always want to be alone. I had tried beating my brother and sisters competence in any areas, yet, i am still a junk....How will i get the trust of my parents and the love i always wanted to feel thesame with my brothers and sisters? What to do?