Reality star Kourtney Kardashian and her boyfriend Scott Disick welcomed their third child Sunday, Us Weekly broke the news.

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The baby boy follows the couple's eldest son, five-year-old Mason, and daughter, two-year-old Penelope.

What's special about the baby boy's birth is that it coincides with Mason's birthday!

"The family is freaking out with joy. What an amazing coincidence," a source close to the mom-of-three told E! News.

Before giving birth, Kardashian shared on Instagram, a picture of a baby doll lying in a crib.

"Nap time! Someone's already using our new crib," the caption said.

Kourtney attracted the world's attention when she posed nude for DuJour magazine and then talked about the joys of expecting that she's going to be a mom for the third time around.

"I had done a nude shoot when I was pregnant with Mason, really last minute just for myself, and I love it," she said in the interview with DuJour, explaining why she opted to get nude on the photo shoot.

"This time, we were shooting for our show, and everyone on our camera crew was like, 'You are so comfortable just walking around naked and pregnant!' [But] what appeals to me is celebrating the shape of my body being pregnant and capturing that time in my life...It's a wonderful thing to be able to show my children these photographs one day and say, 'This was you inside'...I'm at my best when I'm pregnant.," she continued.

"It's such an amazing feeling, the transformation that your body goes through. There's something about that that's so empowering and beautiful."

News of the 35-year-old star's pregnancy hit the news last June, surprising Disick at the debut episode of their reality TV show, Kourtney & Khloe Take the Hamptons.

In an interview with Natural Health magazine for its September/October issue, the star talked about how motherhood made her feel better about herself: "I used to get Google Alerts to be aware of what was being said [about me], but it was just a waste of time," Kardashian said.

 "[My kids] make it really easy for me not to pay attention."

Meanwhile, her sister, Kim Kardashian noted that Kourtney is a low-key mom and she's learned a lot from her parenting style.  She also compared that while she's "fun and playful," Kourtney "does more of an attached parent style where her kids sleep in her bed with her."

TagsScott Disick, Kourtney Kardashian, kourtney kardashian gives birth