Kim Kardashian is now a mother of four. The 38-year-old "Keeping Up with the Kardashians" star took to Twitter Friday after welcoming a baby boy via surrogate with husband Kanye West. "He's here and he's perfect!" she told fans. Kardashian and West are also parents to 5-year-old daughter North, 3-year-old son Saint and 15-month-old daughter Chicago. "He's also Chicago's twin lol I'm sure he will change a lot but now he looks just like her," Kardashian added on Twitter. TMZ said Kardashian's surrogate gave birth Thursday. The baby boy reportedly weighed 6 pounds, 9 ounces. Kardashian's mom, Kris Jenner, and sister Kourtney Kardashian filmed an episode of "The Ellen DeGeneres Show" Thursday, where Kourtney announced Kardashian's surrogate was in labor. Kourtney surprised Jenner with the news after bringing out six of her mom's grandchildren -- Kourtney's kids Mason, 9, Penelope, 6, Reign, 4, and Kardashian's children North, Saint and Chicago. The episode aired Friday. "What are we doing sitting here?" Jenner asked after hearing the news. The "Ellen" segment also featured the daytime host giving each of the children a shirt with a heart that said Lovely, Jenner's nickname. Earlier in the show, Jenner received pink scrubs equipped with a pocket camera to capture everything happening in the delivery room. Kardashian confirmed in January that she was expecting her fourth child with West via surrogate.