No word yet on the child's name nor any other birth details. But the little lord does share a birthday with the E! fashionista's firstborn son, Mason Dash, who turned 5 on Sunday, and joins sister Penelope Scotland, 2.
"The family is freaking out with joy," a source told E! News of the shared birthday. "What an amazing coincidence."
"Happy birthday to the coolest little boy in the entire world," the 35-year-old wrote in an Instagram greeting to Mason. "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."
"Stop growing up! How are you 5 already?!?! My ace! My Mase!" wrote Khloe Kardashian.
"Happy Birthday to the lego master Mason!!!" added
Incidentally, Kardashian and Disick revealed the child's gender on Sunday's episode of "Kourtney and Khloe Take the Hamptons," the family's latest spinoff series on E!.
"I am so happy we're having a boy," she said on the show. "It's going to be perfect for our family."
The star also posed nude for DuJour magazine leading up to the child's arrival.
Reps for Kardashian and Disick did not immediately respond to requests for comment.