Kourtney Kardashian Sunday reportedly welcomed her third child with longtime partner Scott Disick.

E!, which airs the Kardashian reality-show clan's various series, said a baby boy was born the same day as older brother Mason Dash's fifth birthday. Kardashian, 35, and Disick, 31, originally of Eastport, also have a daughter, Penelope Scotland, 2.

Kardashian's representative did not respond to a Newsday request for confirmation.

No name was reported. Kardashian told E! in October that she and Disick had "some ideas" for a name, but added, "I am stuck. . . . I want to wait until the baby is born."

Kardashian, eldest of the three Kardashian sisters, revealed the baby's gender on the Dec. 7 episode of "Kourtney & Khloé Take The Hamptons," which was shot on Long Island throughout spring and summer.

None of the sisters has tweeted about the birth. Kourtney Kardashian Sunday tweeted to her son Mason, "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."

Kim Kardashian, 34, Sunday tweeted, "Happy Birthday to the Lego master Mason!!! You are so big I can't take it! You are my everything! I love you so much!" while Khloé Kardashian, 30, wrote, "Stop growing up! How are you 5 already?!?! My ace! My Mase!"

Kourtney Kardashian said in the December/January issue of Fit Pregnancy that this pregnancy found her "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."