Complex sentence: Dolores and her younger sister Helene made their first film appearances in the years 1909-1915 as child actresses for the Vitagraph Film Company, playing supporting roles in several films starring their father, who was a popular matinee idol at the time.
Split into simpler sentences: Dolores and her younger sister Helene made their first film appearances in the years 1909-1915 as child actresses for the Vitagraph Film Company. They played supporting roles in several films starring their father, who was a popular matinee idol at the time.