New mom JESSICA SIMPSON wants one big happy family — with ex-husband NICK LACHEY and his wife VANESSA MINNILLO!

The 31-year-old "Fashion Star" got the idea after Nick and Vanessa sent a gift basket to her hospital room when she gave birth to fiance ERIC JOHNSON's daughter Maxwell Drew on May 1, sources say.

Now she believes her baby girl will have a ready-made playmate when Nick and Vanessa's child arrives in September, insiders add.

"Being a new mom has made Jessica giddy with love and wanting to share that feeling with the whole world," a close friend told The ENQUIRER.

"She and Nick have had their ups and downs since their divorce, and Jessica and Vanessa have sniped at each other for years. But for Jessica, that's all water under the bridge. She'd love for her daughter and Nick's child to grow up together. She's even called him and Vanessa to tell them so."

After Jessica married Nick in 2002, they became reality TV sensations with their series "Newlyweds: Nick and Jessica." They divorced in 2006, and Nick wed "Wipeout" co-host Vanessa, 31, in July 2011.

While their new relationships have softened some hard feelings, Jessica has gone overboard with her happy family dream, according to another friend.

"Vanessa laughs at the thought of forming a mommy's club with Jessica and becoming her BFF," revealed the source. "She says Jessica is best appreciated from a distance. I think Jess read a little too much into that gift basket Nick and Vanessa sent."