21194773 on Family Tree Circles

My family came to this country in 1821. According to histories of Allegheny County, Pa., William (b. about 1775) and Martha McKinney settled on part of Braddock's Field south of Pittsburgh. Their children made a small fortune when they sold that same land to Andrew Carnegie for his first steel mill in the U.S. -- the Edgar Thomson Works.

Anyway, their children, all born in Ireland, were either adults or almost adults when they landed in the U.S. Their names were John, Robert, Sarah, Mary and Nancy (or Ann).

John (my line) married Rebecca McGlinn.
Robert married first Mary Dick, then Catherine Lannon (name found spelled different ways).
Mary married a Samuel McKinney (hopefully distant, distant cousin).
Nancy married Harvey Chapman.

Of John's children, William (my line) ended up marrying a Josephine Clara West (my line), Martha married a William Curry, Anna a Levi C. Brinton, and Mary a Dr. James Matlack.

My problem has been that long ago there was an unexplained (to me, at least) separation in the family. Aside from my own brother and sister, I know of no living McKinney relations from this line.

William and Josephine had William A. (my grandfather) who married Emma Dout; Charles B., who married Margaret Bott. One other child died in youth, and another died a spinster.

Any help would be appreciated.