There is not any rule that I am aware of for which sibling should receive the cross. I would base it on who finds the most significance or meaning in the cross.
If all 5 siblings equally want it, then you could do one of a couple of things. You could share it, meaning each of you possess it for a length of time and then pass it to the next sibling. You could also determine it by birth order where the oldest receives the cross, or give it to the sibling who was most responsible for the end of life care and funeral planning of the parent.
At my Mother’s funeral the funeral home decided of their own accord to present my Mother’s Cross to my younger sister and had the Deacon declare her the new head of our family, binding our family with an oath being made under God at the Rite of Committal that she is now the head of our family. Our family remains shocked and hurt that the funeral home would do such a thing.
I paid for the services and when I arrived at the funeral and asked what was planned they refused to tell me this part… said it had nothing to do with me.
I sincerely hope you have not gone through such a hurtful ordeal at a loved one’s funeral.