Kris Jenner pens sweet birthday note for firstborn Kourtney Kardashian

Kris Jenner extended heartfelt birthday wishes to her firstborn daughter, Kourtney Kardashian.

The momager of the Kardashian-Jenner clan shared a series of adorable photos of the birthday girl alongside a sweet caption.

She began her note by saying, "Happy birthday to my firstborn babydoll @kourtneykardash!!!!!! What in the world is happening, time is twirling so fast and I can’t believe you are 45!!!"

Kris shared a sweet memory of little Kourtney who grew up into the most amazing woman.

She stated, "It seems like just the other day you were wearing your 5 year old party hat going to Buckley to be the line leader and I was bringing cupcakes for the class to celebrate."

The socialite said that her daughter "has grown into the most beautiful and amazing daughter, wife, mommy, sister, auntie and best friend a girl can have."

Speaking of Kourtney's business venture Poosh, Kris shared, "You are a kick ass business boss and I am so proud of you every day!"

"Thank you for making me a grandma for the first time and for every single moment and memory we share. I love you beyond measure," the reality TV star concluded her note.