Christina Aguilera and Nicole Richie have become fast friends since giving birth to their first children, Max and Harlow, respectively, just one day apart in January 2008.

In fact, the petite powerhouse and former television reality star have so much fun together during their weekly play dates, they are thinking of creating a Mommy & Me Club for other celebrities and their young children.

“The call each other about how to get their babies to stop crying, how to get them to sleep, dirty diapers, and organic baby food,” a Hollywood tattle reveals in the March 9 issue of The National Enquirer. “Their babies may have brought them closer….”

Christina, 28, and Nicole, who at 27 is expecting a second child with BF Joel Madden, believe their fellow celebrity moms could also benefit from the exchange of potty-training secrets and tips for dealing with toddlers.

“They find it so helpful that they think there’s a need for a club for celebrity moms,” The Enquirer source says of Nicole and Xtina’s bond over motherhood.