Katie Holmes , the star of Mad Money, 29, has been moving more and more into the role of mother to Nicole Kidman's stepchildren Isabella, 15, and Connor, 13. "They call me Mom," she tells Parade.

Now Us Weekly reports this coincides with 40-year-old Kidman's confession on a British TV show that her two kids with Tom Cruise no longer "call me Mummy."

"It's Mum or sometimes Nicole. I'm like, 'Hey!'" she said. (Kidman's rep tells Us she was only "joking around.")

"Isabella especially took to [Katie] right away," a source close to the family tells Us.

Adding to the tension is the fact that Cruise is raising his children as Scientologists.