Hello. I too am a descendant of William Shinnick (1840-1911) and Mary M. Allen (1846-1927).
They were my g-g-grandparents. (I have her middle name as "Marguerite" instead of "Margaret", but who knows?)
This is my branch, fathers to sons: William Shinnick (1840-1911)--> Joseph Herman Shinnick (1875-1958) --> William Lloyd Shinnick (1909-1960) --> Joseph Norton Shinnick (1938-) --> ME, Robertson William Shinnick (1965-)--> Justice Robertson Shinnick (1991-).
What little I know about our Shinnick branch only goes back to 1840, with the first William Shinnick's birth (in Ireland, according to my information).
You can find more detailed information here, hopefully some of which will help: http://www.shinnick.org/william2.htm
(I have no affiliation with that site but am grateful to the Shinnick who created it).
I am trying to fill in the blanks and follow my Shinnick ancestors further back, of course, if any of you are able to help!
~ Rob (Robertson William Shinnick)