Gregg family from Donegal to Pennsylvania

I wrote earlier of James McKnight and Ellen Gregg who arrived in New York from Londonderry on board the Hannah Thornton in 1849.  Since then I have James’ will which names as his executor his nephew Joseph B Gregg.  This led me to find Joseph’s father, Nesbitt and then his brothers, a sister and parents.  It seems most if not all of the Gregg family migrated to America in the 1840s and that James McKnight, his wife Ellen Gregg, their children and his sister Jane McKnight, followed them.  As usual if anybody knows anymore about any of these families or has photographs, documents etc please get in touch.  I know the Gregg families had large families in Pennsylvania and New York.