The slave who was the subject of Prigg vs. Pennsylvania was named Margaret Morgan. Her master was another woman named Margaret Ashmore, a citizen of Maryland. In 1832, Morgan escaped and travelled to Pennsylvania where she gave birth to several children, one of whom was born a year after her escape.
Edward Prigg, a slave catcher acting as Margaret Ashmore's agent, seized Morgan and brought her before a Pennsylvania magistrate, who refused to hear the case. He thereafter carried her to Maryland where a Maryland court determined that Morgan was a runaway, and returned her to Ashmore. Thereafter, Prigg was convicted of kidnapping in a Pennsylvania Court. The Pennsylvania Supreme Court affirmed his conviction and the case was appealed by both Pennsylvania and Maryland to the U.S. Supreme Court.
The U.S. Supreme Court relying on the full faith and credit clause of the Constitution held Pennsylvania's Fugitive Slave Law unconstitutional:
The Constitution does not stop at a mere annunciation of the rights of the owner to seize his absconding or fugitive slave in the State to which he may have fled. If it had done so, it would have left the owner of the slave, in many cases, utterly without any adequate redress.
The Constitution declares that the fugitive slave shall be delivered up on claim of the party to whom service or labor may be due. It is exceedingly difficult, if not impracticable, to read this language and not to feel that it contemplated some further remedial redress than that which might be administered at the hand of the owner himself. "A claim" is to be made.
"A claim," in a just juridical sense, is a demand of some matter as of right, made by one person upon another to do or to forbear to do some act or thing as a matter of duty.
It cannot well be doubted that the Constitution requires the delivery of the fugitive on the claim of the master, and the natural inference certainly is that the National Government is clothed with the appropriate authority and functions to enforce it. The fundamental principle applicable to all cases of this sort would seem to be that, where the end is required, the means are given, and where the duty is enjoined, the ability to perform it is contemplated to exist on the part of the functionaries to whom it is entrusted.
No information is available about Margaret Morgan's children, although the safest assumption is that since they were the children of a slave, they were the lawful property of the slave owner.