We are related to Westray Stevensons, this is the family:
George STEVENSON of Bu (or Bull also in records as Bowl), Westray
+Ann SEATTER married August 04, 1824
George Seator STEVENSON
Ann Traill STEVENSON
Stewart STEVENSON (Female)
+ Jeremiah (Jerome) Rendall c. Nov. 20, 1829 of Gaird Cottage. The couple was married in Firth but were both from Westray. George Stevenson remarried and moved to Finstown after his first wife died in child birth, Mary went with him. Jeremiah might have followed Mary. The couple lived in Rendall parish (apparently) for a few years and then probably moved to Ontario.
Is the above William your William? Also, do you know Valerie Aitchison of Wellington NZ? Her husband's family are decendants of Barbara Stevenson.