Although my records don't show a Helena as a daughter of this family, I do have relatives John Fullerton & Margaret Taylor, who emigrated to Canada about 1850. The oldest children (Matthew & Ann) were born in Ireland, the younger ones were born in Canada (Letitia, Mary Jane, John, Thomas, George). The family lived in Sullivan Township. The Fullertons were from Scotland originally but actually emigrated from Ireland.
Do any of these names sound like ones in your family tree? If you can give me details about the marriage record (esp.witnesses), I can see if I recognize anyone.