My great-great grandmother, Nancy Anne (Crowe) Pitts was the daughter of first cousins and granddaughter of Daniel Robert Crowe and Anne Susannah Shelton, an obvious example of pedigree collapse.
My great-grandparents, Sarah Elizabeth Pitts and Thomas Eli Profitt, were 13th cousins, once removed, descended from John Trelawney.
My great-great grandparents, Nancy Carolyn Cox and Stephen Sewell Profitt, were 14th cousins, once removed, descended from John Wadham.
I still have to prove if my 4x great grandfather, John Alexander, born about 1774, was descended from two related Alexander lines. as his father John Alexander (descended form John Alexander of Eredy born in Scotland) and his mother Mary Hines (descended from Richard Alexander born in Ulster, Ireland, but supposedly descended from the Alexanders of Menstrie, Clackmannanshire, Scotland). I have no paper trail on the latter case.
I'm sure that all of us have inbred ancestors at some point in time.