For years it used to bother me that my mother had beautiful pictures of all her other children in gold and silver frames and all she had of me was an ugly black and white passport sized photo stuck in the corner of one of the other frames.
It doesn't bother me anymore.
Sometimes parents love some kids more than others. It is a fact of life that happens. I cannot stop my mother from loving my siblings more than she loves me, all I can do is accept it and move on with my life.
You already understand that your father holds some members of your family in poor regard and there is very little you will ever be able to do to change it.I guess you already know that.
In time you will learn to let go of the pain that the people we love and care about can cause us.