I am also related to Sarah Osborne through her son Joseph. My aunt wrote this about the line:
"We are descended from the line of Robert Prince and Sarah Warren (the witch). They had two sons, James and Joseph. His son Joseph (born 1698)was the father of Timothy, (1722)who was the father of Samuel, (1745)who was the father of Orland, (1787) who was the father of David, (1822) who was my great grandfather. His daughter Marie (or May) was my grandmother, her son was my father Truman and your grandfather."
So, since I am one generation later than my aunt, Sarah Osborne was my 7th great grandmother.
Thanks, Thalia Moore
PS Or it she my sixth great grandmother? I have trouble counting the generations!