It appears Margaret (McNabb) Shrader is the son of John McNabb and Mary Young. John McNabb appears to be the son of William McNabb and Margaret Mitchell.
Sources:
From the "History of Juniata Valley and it's People":
(I) William McNabb, his great-grandfather, came to America from
Ireland in the latter part of the eighteenth century, and settled in the
eastern part of Pennsylvania, after a voyage of three months' duration.
He died in Derry township, Mifflin county, Pennsylvania, at the age
of about seventy years. He married Margaret Mitchell, who had come
HISTORY OF THE JUNIATA VALLEY 1225
to America on the same vessel. They had children: Rohert ; John;
William, see forward; James.
https://archive.org/stream/historyofjuniata03jord/historyofjuniata03jord_djvu.txt
From "This History of Macon County, Illinois":
E McNABB architect and builder was born in Centre county Pennsylvania on the seventeenth of September 1823. His ancestors were Scotch and emigrated to the north of Ireland at the time of the religious persecution which drove so many Protestants from Scotland His grandfather came to America shortly after the Revolutionary war he married a woman of Irish descent by the name of Mitchell. John McNabb the father of the subject of this sketch was born in Pennsylvania and married Mary Young a native of the same state. John McNabb was a mechanic but after his removal to Richland now Ashland county Ohio in the year 1834 he engaged in farming. He died in that county as did also Mr McNabb's mother. The subject of this biographical sketch was the seventh of ten children...
link to source: https://books.google.com/books?id=RP1LAQAAMAAJ&pg=PA149&lpg=PA149&dq=john+mcnabb+centre+county+pennsylvania&source=bl&ots=blICTkKrhk&sig=ACfU3U3ijj87aW2HZD5IF2-5EPU1VUCQhg&hl=en&sa=X&ved=2ahUKEwjFicHJ1qboAhXTmHIEHZRRCwMQ6AEwAHoECAgQAQ#v=onepage&q=john%20mcnabb%20centre%20county%20pennsylvania&f=false
Similarly, from "History of Dekalb County, Indiana":
Warren McNabb is a native of DeKalb county in which he spent his entire life his birth having occurred there on July 26 1857 His parents David and Sophia Dunfee McNabb were among the early settlers of the county David was a native of Center county Pennsylvania born December 9 1819 and was a son of John and Mary Young McNabb also a native of that state the father being of Scotch descent and the mother of Swiss and English ancestry W hen David McNabb was but thirteen years of age the family moved to Ashland county Ohio where they remained until 1843 when they came to DeKalb county Indiana and entered eighty acres of wild land in section 35 Fairfield township There he built a cabin home in which
https://books.google.com/books?id=sgQUAQAAMAAJ&pg=PA422&lpg=PA422&dq=john+mcnabb+centre+county+pennsylvania&source=bl&ots=yL9XMqgsb5&sig=ACfU3U3E0jZ8YH-QoDRuwbAnxOb2EG8Weg&hl=en&sa=X&ved=2ahUKEwjFicHJ1qboAhXTmHIEHZRRCwMQ6AEwBHoECAoQAQ#v=onepage&q=john%20mcnabb%20centre%20county%20pennsylvania&f=false
And one more account:
Looking for any information on Mitchell family who were linen merchants in Londonderry in the 17760s-80s & beyond - possible gentry? Daughter Margaret Mitchell b. 1761 ran away with a man to Philadelphia. She ended up marring another man she met on the vessel, William McNabb also form Londonderry.
Decades later (1820s) her family tried to claim a considerable inheritance from the Mitchell estate but could not prove she was indeed a Mitchell heir as she never signed her name as such.
I know- a crock? but that is the story - looking for any clues!
https://www.genealogy.com/forum/regional/countries/topics/ireland/londonderry/1522/
