Listen to Hit Nation Radio on iHeartRadio

Hit Nation Radio

There's one more Kardashian for fans to keep up with. Kourtney Kardashian and her longtime boyfriend Scott Disick welcomed their new son into the world on Sunday ... on their son Mason's 5th birthday!  

A source tells E! News, "The family is freaking out with joy. What an amazing coincidence."

The new baby boy is their third child together, and is now a little brother to Mason and daughter Penelope -- who is 2 years old. 

Earlier this month, the reality star made news for posing nude on the cover of Du Jour magazine. 

Meanwhile on top of getting a new little brother for his birthday, Mason was treated to a 5th birthday surprise from Aunt Kim! The 5-year-old, his sister Penelope, and cousin North all enjoyed "Disney On Ice."

Disney on Ice #Mason #Zeplin #Penelope #North #BestFriends

A photo posted by Kim Kardashian West (@kimkardashian) on

And although Kourtney and Scott were recovering after welcoming their new bundle of joy into the world and couldn't be at "Disney On Ice" themselves, Kourtney posted a sweet message to Instagram for her oldest on his birthday. She said:

"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."

Photo: Getty Images