Complex sentence: She was the first of the Howard-Gibbon siblings to emigrate to Ontario, Canada, where she began teaching in Saint Thomas, and later moved to Sarnia and continued to teach children there for many years.
Split into simpler sentences: She was the first of the Howard-Gibbon siblings to emigrate to Ontario, where she began teaching in St. Thomas. She later moved to Sarnia and continued to teach children there for many years.