Do you have Registration of Death for Thomas SINCLAIR - This may show the names of parents if known to the informant.
Parents of Elizabeth WHITFORD were Joseph WHITFORD and Ellen WHITFORD nee KENNEDY
You know children
Elizabeth SINCLAIR married George STARR
Ellen Agatha SINCLAIR married Alexandr LETANDRE
Caroline SINCLAIR married Charles MAYO
Harriet married Hugh McDONALD
are you in contact with any of the above families ?
Do you know if any stayed in Manitoba ?
Perhaps family member/s may have sumitted family history/stories to a Local History book project.