Joel & Nicole's Santa Baby

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At the Nov. 22 Good Charlotte CD Release Party at the Ecco Ultra Lounge in Hollywood, Joel Madden told OK! he is utterly devoted to his 11-month-old daughter, Harlow.

"My whole life is centered around her," he said. In fact, a pal tells OK! that Joel, 29, and fiance Nicole Richie, 27, are creating a winter wonderland for their baby girl this Christmas. And why not? Her middle name is Winter!

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"They got fake snow for the windows and Joel joked that he could dress as Santa!" the friend tells OK!.

Meanwhile, Nicole has been making sure to keep Joel's twin brother, newly single Benji Madden, company since his split with Paris Hilton. The former Simple Life star stayed close to Benji at the Good Charlotte Release Party, pulling him in for hugs and photo ops with Joel throughout the night.

An fellow party-goer tells OK!, "she was very protective of him. She seemed to be genuinely concerned that he was having a good time."