This is a good question -- all counties have the Orphan's Court. This is the explanation on the Philadelphia Orphan's Court website.

"The Orphans' Court serves to protect the personal and property rights of all persons and entities that may not be otherwise capable of handling their own affairs. The jurisdiction of the Orphans' Court includes matters concerning minors, incapacitated persons, decedents' estates, nonprofit corporations and trusts. Additionally, the Court has the authority to settle any dispute or issue that may arise in connection to the application for a marriage license through the Philadelphia Marriage License Bureau. It is the main focus of the Orphans' Court, in all the above-mentioned matters, to ensure that the best interests of the person or entity are not compromised. In fact, the name of the Court is derived from the general definition of "orphan" as one lacking protection, not the common association of a child deprived by death of his parents."

It was common practice in Pennsylvania for minors to ask for a guardian; especially if the widow was remarried. The guardian was expected to help protect the minor's rights to the father's estate.

I have several families where the Orphan's Court records have been useful.

As for James and Rachel McCoy, I haven't anything new to add. The only possible thread to pull is that of Jonathan Phillips; he was guardian for James McCoy's sons, he acted as agent for William McCoy when the land in Allegheny County was sold. He bought land in 1804 from Margaret McCoy, widow of a William McCoy---perhaps we have all been barking up the wrong tree for years and should be looking at this William McCoy and not for the mythical Alexander!