Guardian Of The Estate Vs. Person

My sister, a single parent, died in PA last year. She had a will and spoke extensively to us about her wishes, and we've followed it. My partner and I adopted her child in NC, my sibling was to be the executor of the will and the custodian of the child's estate. They decided not to probate the will because there was not much point when we found out about her extensive gambling debts and bankruptcy.

Now that the adoption is final, we have an account set up for the child and attempted to get their share of a life insurance for them. The company will only release the funds to the guardian of the estate, not the guardian of the person. My sibling will do whatever is necessary as will we.

What is the best way for us to become the guardian of the estate (or at bare minimum for someone to be able to get this child the money they are due)?