Simplify the following text for a Grade 10 native English-speaking person.
Original: His mother was at first against the marriage because she looked down on Sophia Dorothea 's mother ( who was not of royal birth ) , and because she was concerned by Sophia Dorothea 's legitimated status .
Simplified: The marriage was ended in 1694 , on the grounds that Sophia Dorothea had effectively abandoned George . Sophia Dorothea 's father , George William , and George Louis , had Sophia Dorothea imprisoned in Ahlden Castle in Celle , where she was unable to see her father , former husband , or children .