They grow up so fast!

Monday marks the second birthday of Harlow Winter Kate Madden-- the adorable daughter to celeb couple Nicole Richie and Joel Madden.

And Richie, 28, isn't about to let the special day go by without a lot of fanfare. The L.A.-based star  Tweeted before 6 a.m. on Monday: "Up super early sneaking around the house in the dark setting up surprises for when my birthday girl wakes up!"

Harlow's daddy Madden, 30, was up even earlier (or perhaps had simply stayed awake) to Tweet an affectionate greeting: "Happy Birthday to the most beautiful little girl in the world. Harlow makes me proud every. single. Day. i'm blessed." The Good Charlotte singer and Richie have been together since late 2006. Also celebrating with Harlow? Her baby brother Sparrow James Midnight Madden, 4 months.

The famous family had another star well-wisher: Khloe Kardashian. "Happy Birthday Harlow!!!" Kardashian, 25, Tweeted Monday morning.

Shortly after Sparrow's September 9 birth, proud grandfather Lionel Richie told Larry King that his daughter was "the happiest person I have met in my life...Right now, she's just in total control. I'm the one that's nervous. I'm Grandpa."