Kourtney Kardashian shared the first glimpse of her newborn son on Instagram, one week after giving birth.

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In the photo posted on Sunday, the 35-year-old is seen holding the baby's little hand.

Kardashian also revealed her third child's name in the caption, writing, "Madly in love with my little Reign Aston Disick."

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 Madly in love with my little Reign Aston Disick.

A photo posted by Kourtney Kardashian (@kourtneykardash) on Dec 12, 2014 at 8:36am PST

The Kourtney and Khloe Take The Hamptons star welcomed her third child with longtime boyfriend Scott Disick on Dec. 14, the same day as her son Mason's fifth birthday. That day, Kardashian shared a photo of their eldest child on Instagram with a sentimental caption.

"Happy birthday to the coolest little boy in the entire world. You teach me so much every single day and changed my universe the second I met you. You have taught me what life is all about and I am truly blessed and honored to be your mommy," wrote Kardashian who is also mother to 2-year-old daughter Penelope.