Kourtney Kardashian, son Mason, and daughter Penelope
Kourtney Kardashian has become a mother for a third time.sweetkardashians/tumblr

Kourtney Kardashian has given birth to a boy.

The reality TV star's third child with her partner Scott Disick arrived on Sunday (14 December) the same day as her eldest son Mason who celebrates his fifth birthday.

A source close the family told E! News: "The family is freaking out with joy. What an amazing coincidence."

As well as Mason, the couple have a two-year-old daughter named Penelope.

Just a day earlier, The Keeping Up With the Kardashians star posted an image on Instagram of a doll lying in a crib, hinting that the baby's arrival was imminent,.

She captioned the picture: "Nap time! Someone's already using our new crib."

Earlier in the week, Kourtney's mother Kris Jenner told E! the new baby could arrive at any time. "We're days away. I may be going from here to the hospital," she said.

Just hours after the birth of her third child, Kourtney turned to Twitter to wish Mason a happy birthday.

Scott Disick Kourtney Kardashian
Kourtney and Scott Disick have welcomed a son.Getty

Posting a picture of the birthday boy giving the thumbs up, she wrote: "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 honoured to be your mommy."

In a recent interview with Fit Pregnancy, the 35-year-old spoke about the experience of her third pregnancy.

She said: 'I love being pregnant in general. This time I'm more tired than I was the other times. I think it's because I'm always running around and working on different things. But I feel comfortable with how I look and feel. I find a pregnant body to be beautiful and an incredible reminder of what a woman's body is made to do."

Her long-term partner Scott Disick had initially expressed his apprehension at the news that he was due to become a father for the third time. Kourtney to said she feared her pregnancy had put pressure on her relationship.