UPDATE: E! News has learned celebrity party planner Mindy Weiss helped create an "alien kinda night" with love lanters, UFOs, inflatables and more.
Somebody is feeling the birthday love!
In several social media posts from Saturday evening, the Keeping Up With the Kardashians stars couldn't help but kiss and hug Kourtney Kardashian and Scott Disick's youngest child as they all played in the backyard.
"Me as a mom," Kendall wrote on social media with a bounce house and other inflatables visible in the background. Kylie later posted an Instagram where she held baby Reign extra tight.
"I love you baby angel," she wrote as Reign wore a denim jacket and black beanie. "The cool aunts."
While it's too soon to tell if this was an actual birthday party, E! News has learned model Jordyn Woods and artist Harry Hudson were also at the house for a fun afternoon that included alien laser tag.
This weekend is expected to be quite the busy one for Kourtney as Mason Disick's birthday also falls on Monday.
Before any birthday celebrations could begin, however, the proud mom spent part of her Friday night at The Nice Guy in West Hollywood. While working an all-white ensemble, the reality star was spotted chatting it up with family friend Justin Bieber.
A source told E! News that the pair spent time on the patio together before the "Sorry" singer had a surprise performance in the popular A-list venue. And before any romance rumors or speculation starts about these two, a separate insider assured us that there is "nothing going on" between the pair.
New episodes of Keeping Up With the Kardashians air Sunday nights at 9 p.m. only on E!
—Reporting by Sara Kitnick
(Originally published Saturday, Dec 12, 2015 at 8:06 p.m. PST)