The singer shared an adorable snap of the event, which included green and pink balloons and a decorated cake – too cute!
“Congrats Big Sis! #bigsisterparty,” the 37-year-old singer captioned the pic.
Not one to shy away from social media, Pink made her big pregnancy announcement back in November with a simple ‘Surprise!’ and has since been documenting her blossoming belly with cute snaps, often with Willow by her side.
After welcoming son Jameson Moon Hart into the world on the December 26 last year, Pink and hubby Carey Hart's family is now complete.
As for the interesting name? Pink revealed to Access Hollywood way back in November 2010 that she'd already picked out her future bub's name.
“My dad’s name is James, and my brother’s name is Jason. [Carey and I] are both Irish, Carey’s middle name is Jason, and Jameson — we like whiskey. That’s a no brainer.”
Pink and her retired motorcycle racer husband have also just celebrated their 11th wedding anniversary but after a rocky start including two separations, it doesn’t look like they'll be going their separate ways again now they have the perfect little family of four.