Cynthia Brisby is Jonathan and Mrs. Brisby's youngest child and Teresa and Martin and Timothy's younger sister in The Secret of NIMH. She was voiced by Jodi Hicks as a 4 year old and Whitney Claire Kaufman as an 8 year old. In the movie, Cynthia is the 3rd child but, in the book, Cynthia is the youngest and last child of the Brisby family.