Simplify the following text for a Grade 6 native English-speaking person.
Original: There is manuscript evidence that Austen continued to work on these pieces as late as the period 1809 â `` 11 , and that her niece and nephew , Anna and James Edward Austen , made further additions as late as 1814 .
Simplified: There is some proof that Austen continued to work on these pieces later in life . Her nephew and niece , James Edward and Anna Austen , may have made further additions to her work in around 1814 .