Katie Holmes wants sole custody of her daughter because she fears being cut out of her life.
The actress filed for divorce from husband Tom Cruise a week ago in New York, asking for sole custody of their six-year-old daughter Suri, and it has been claimed she is worried if she shares custody she could end up being phased out of her child's life.
Katie is said to be determined to win the custody battle after seeing how little contact Tom's adopted children, Bella, 19, and Connor, 17, have with their mother, the actor's second wife Nicole Kidman.
A source told the Daily Mirror newspaper: "Bella and Connor aren't that close to Nicole, and Katie is determined that she won't be cut out of Suri's life.
"Katie will not be relegated to a secondary role in her daughter's life. Period. And she is prepared to fight Tom in court.
"Katie isn't going to back down and she will do whatever it takes to ensure that she raises Suri herself."
Katie is also believed to be worried about the influence the sci-fi cult Scientology, of which Tom is a devotee, could have on Suri.
The source added: "Bella and Connor are devoted to their father and Scientology, and Katie saw this first hand, and this is one of the reasons she filed for sole custody."
Katie, 33, has also filed for divorce in New York, as part of her strategy to win sole custody, as she believes courts in Los Angeles - the city where she lived with her husband - will favour joint custody.
Her break-up from Tom, 50, is said to have been meticulously planned, with her giving no clues she was going to leave her husband until the last minute.
The source explained: "She was talking to Tom on the phone up until last week saying, 'I love you.'
"Her inner circle has been planning this and switching out cell phones since she was in China (in mid-June).
"When new cell phones arrived, then nobody could reach her.
"Her old best friends from last week don't have her new number, no email. She's unreachable."