They were down for the count, instantly smitten, love at first sight.
The birth of Mason Disick, also Kris Jenner's first grandchild, not only officially meant the arrival of the Kardashian family's next generation, but it also sparked the stirrings of maternal instincts in all three Kardashian sisters.
"Kourtney didn't even like kids," Kim told Ryan Seacrestat the time. "I never thought she'd ever want to have a baby." But "I think Kourt's going to be the most amazing mom."
That prediction certainly came to pass. And with the next generation now numbering six as of today with the arrival of Blac Chynaand Rob Kardashian's first child together, daughter Dream Kardashian, you couldn't imagine a more loving, doting, devoted and protective trio of moms and aunts than Kim, Kourtney and Khloe.
Let's just say... Dream hit the auntie jackpot.
"I love everything about being an aunt," Khloe mused last year in a post on her app, when she was already an all-star babysitter, confidante and cuddle buddy to Mason, Penelope and Reign Disick and North West, and Kim's son Saint was on the way.
"They say it takes a village to raise a child—that couldn't be more true," she said. "We all have so much fun helping raise each other's kids."
Sure enough, first out of the gate on social media this morning after Dream was delivered was Khloe, who tweeted, "My new niece is absolutely stunning!!! So thankful I was able to land in time to witness this miracle happen! Praise God!"
My new niece is absolutely stunning!!! So thankful I was able to land in time to witness this miracle happen! Praise God! ????— Khloé (@khloekardashian) November 10, 2016
As Kourtney's firstborn, and the first nephew for Kim and Khloe, Mason—who somehow is going to be 7(!) next month—was the little prince from day one, reaping the rewards of being surrounded by an already huge family that was ecstatic for his arrival.
Kim especially got to spend a lot of time with her nephew when she and Kourtney lived in Miami together back in 2010, the new aunt spotted regularly around town with baby Mason in his stroller.
And after two years of having them to himself, all of Mason's aunts made sure that he still felt extra-special when sister Penelope arrived in July 2012. Kim, Khloe and Kendall and Kylie Jennertook him to the circus after Kourtney gave birth to baby No. 2—and it sounds as though Kim and Khloe were helping out with the big-brother pep talks ahead of time.
"I can't wait to spoil little Penelope," Kim wrote on her blog at the time. "I know Mason is going to be the best big brother in the whole world."
Khloe gushed accordingly as well. "The entire family is literally exploding with joy and have not stopped fawning over our new little girl," she wrote the day after Penelope arrived. "And Mason is already loving being a big brother! This is just such a special and happy time for my family. Thank you to Kourt and Scott for making such beautiful babies!"
Though speaking of sibling rivalry, Kim and Khloe have actually enjoyed some friendly competition over who's the coolest aunt.
When Khloe tweeted about Mason's first sleepover at her house last year, possibly his first night away from his mom's house in L.A., Kim protested, "Ummmm his first sleepover was with me in NYC... Nice try."
"Lol Kourts the one who told me that it was his first!!!@kourtneykardash set the record straight woman!!" Khloe insisted. (It's OK, Khloe, you may have nudged ahead in the race with that rockin' jam session.)
Aunts KoKo and Kim readily stepped in to help Kourtney out after she ended her romantic relationship with her kids' dad, Scott Disick, taking Mason and Penelope on a road trip with North and providing constant moral support as Kourtney figured out her next move. Kim also took Mason with her to New York over the July 4 weekend so Penelope could get some alone time with Kourt during that tough time.
Penelope and Khloe have also made for a formidable pair, from the mermaid moments and the matching outfits and hairdos to just the glee on KoKo's face whenever she gets to spend quality time with Princess P.
Meanwhile, the auntie bond is just as strong between Khloe and Kim's kids, Khloe even keeping up with North when she was a baby via FaceTime when she couldn't be there in person.
"Face time session with Nori and KiKi. I mean...her cuteness is unreal. My baby!!! #AuntieKoKo," Khloe memorably logged one of their sessions on Instagram in 2014. "Someone won't go back to sleep. #Cutie."
And when Saint was born, Khloe raved, "He is so cute and so perfect. I love him."
Khloe has also said that, if she has kids of her own, she plans on still being a "fun mom"—just as she's proudly a "really fun aunt."
"I like to have fun and be silly and not take myself too seriously with the kids, so I hope that will translate when I actually have my own," she told Refinery 29 last year.
It was equally important for Kim and Kourtney that their children be as close as they are, and so far it seems that any one of the little ones is just as likely to be hanging with their aunts—or featured on one of their aunt's social media accounts—than they are to be with their own parents.
Kourtney reveled in Penelope and North playing dress-up together, recalling to Harper's Bazaar last year how the cousins were "fighting over shoes" in Penelope's closet but then they quickly arrived at a truce.
"By the end they were sharing and trying the shoes on each other and having so much fun. It reminds me of how Kim and I were when we were little girls," Kourt said.
"Happy Birthday to the sweetest baby Reign. Explaining to Mason that his little brother wanted to be just like him that he even took his birthday was a fun task lol I can't wait for you & Saint to be bff's!" Kim, who had just given birth to Saint a week prior, wrote on Instagram for Reign's first birthday last year—a birthday, by the way, that he shares with his big brother Mason.
And for Mason, Kim posted a picture of the two of them together, aunt and beloved nephew, and in her caption she noted, "You were the 1st born and changed everything!"
To put it mildly.
Welcome to the world, Dream Renee Kardashian. No matter what, you can always be sure that you have a family that loves you more than words can possibly express.
Watch the series premiere of Rob & Chyna Monday Sept. 12 at 9:30pm, only on E!