The 10 Biggest Kardashian Moments of 2018, from Kylie's Pregnancy to Tristan's Cheating Scandal

Though PEOPLE first confirmed the news of Kylie Jenner and Travis Scott's baby on the way in September 2017, she didn't publicly address it until after she gave birth to daughter Stormi Webster on Feb. 1.

"I'm sorry for keeping you in the dark through all the assumptions," she wrote to fans on Instagram. "My pregnancy was one I chose not to do in front of the world. I knew for myself I needed to prepare for this role of a lifetime in the most positive, stress free, and healthy way I knew how."

Stormi wasn't the only addition to the famous family: Kim Kardashian West welcomed her third child with Kanye West, daughter Chicago, via surrogacy on Jan. 15, and Khloé Kardashian welcomed her first child, daughter True, with Tristan Thompson on April 12.

The sisters refer to them as "the triplets," and a source previously told PEOPLE the multiple pregnancies brought them closer together. "There is no jealousy here," said the source. "No one is worried about anyone stealing their thunder. They're focusing on the babies. Everyone is genuinely happy about what's happening."

True's birth came just days after news broke that Thompson had cheated on Khloé during her pregnancy. The new mom ultimately stood by her man and they spent the summer rebuilding their relationship, though she later admitted that the situation was "humiliating."

"My biggest fear was to be selfish and emotional (all understandable under these circumstances) during this time," she wrote in the comments section of a since-deleted Instagram post. "I had to have a lot of talks within myself to keep calm. I want True to look back at her baby photo albums and see love and complete bliss! She deserved to have her family in the room while she took her first breath!"

Their explosive fight dominated the season premiere of Keeping Up with the Kardashians, with Kim infamously calling her sister "the least exciting to look at" after she refused to be accommodating while scheduling a family photo shoot. (Always one to speak her mind, Kourtney said she was "ashamed" of her "disgusting" family in response.)

Though Kourtney told PEOPLE that the confrontation was probably the "craziest fight" they've ever had, sources said the dust did eventually settle. "This isn't some major feud," said one insider. "These sisters have always been able to dish it out and take it. And yes, of course they know the arguments and fights make for good TV."

Ahead of her 21st birthday in August, Forbes dove deep into Kylie's $800 million cosmetics empire, predicting that she's on track to become the "youngest self-made billionaire ever, male or female" — surpassing even Facebook founder Mark Zuckerberg, who became a billionaire at age 23.

According to Forbes, Kylie's namesake company has sold more than $630 million worth of makeup since its initial launch. Combining all of the mogul's profits, Forbes estimates the brand alone is worth nearly $800 million, which Kylie maintains sole ownership of. And that's not even all of her earnings: She also rakes in product endorsements, cashes in her KUWTK paychecks, and boasts clothing lines and brand deals.

Usually the most private of the sisters, Kendall addressed long-circulated online rumors that she's gay in an April Vogue cover interview. "It was a thing for a minute because no one ever saw me with a guy," she said. "I would always go that extra mile to be low-key with guys, sneaking around all the time. You don't want to, like, look crazy."

"I don't think I have a bisexual or gay bone in my body, but I don't know! Who knows?!" she continued. "I'm all down for experience — not against it whatsoever — but I've never been there before."

In August, Kourtney called it quits with Younes Bendjima, her first public boyfriend since her nine-year relationship with Scott Disick. In the wake of their split, a source told PEOPLE that the relationship drove a wedge between Kourtney and her family.

"Kourtney was always so private and closed off when it came to Younes, and that really distanced herself from her sisters," the source said. "Things are fine with them now and I'm sure they'll get even more back to normal now that it seems he's out of the picture for good."

Disick's relationship with 20-year-old Sofia Richie was finally addressed on this season of KUWTK. After Disick and Kourtney got into a bitter argument when he introduced their kids to Richie without giving their mother a head's up first, he apologized and promised to be more considerate.

These days, Richie is still navigating the complicated Kardashian family dynamics, but a source recently told PEOPLE that she's glad to have built up some trust with Kourtney. "Sofia is happy that she has proved to Kourtney that she's great with her kids," the source said. "She loves Scott and wants to be with him."

Kylie shocked fans when she revealed in July that she had dissolved all of her lip fillers. At the time, a source told PEOPLE the new mom had become "much more relaxed and natural" after Stormi's birth. "She's not spending as many hours as she did before to focus on herself," said the source. "And Kylie has never been big on getting dressed up — she's much more comfortable in t-shirts and cozy pants."

That said, the toned-down lips didn't last long. In October, the makeup mogul confirmed she was once again plumping her pout, showing off her "lip touch up" on Instagram.

She barely even drinks now, but Kim recently revealed she's had her fair share of "wild" times. On an episode of KUWTK last month, she admitted she was high on ecstasy when she wed music producer Damon Thomas in 2000 and when she made a sex tape with Ray J in 2003.

Mom Kris Jenner put an end to her dabbling. "She was just so upset thinking that I was going to turn into something and be this crazy drug addict," Kim later revealed. "And I was just like, 'You know what, she's so right. I'm so over it. This is so not me.' And I just never did anything again."