Paris Hilton has remained a fixture in pop culture since the late 1990s, and all along the way, her sister Nicky Hilton has been by her side.

The great-granddaughters of Hilton Hotels founder Conrad Hilton, Paris and Nicky were born into a family dynasty and took their places as “it girls” in the early 2000s. Though Paris was more visible of the two (she famously starred in the reality show The Simple Life alongside Nicole Richie), they’ve both gone on to have success in various business ventures in real estate and fashion design.

Only two years apart in age (Paris was born in 1981 and Nicky in 1983), the sisters have reached milestones such as marriage and motherhood in tandem, helping their bond to grow even stronger.

Kathy, Nicky and Paris Hilton in Los Angeles circa 1985.Donaldson Collection/Michael Ochs Archives/Getty

“I love how elegant and classy you are and strong, and that you stick up for yourself,” Paris told her sister during a TikTok live stream in January 2021. “You never let anyone take advantage of you and you’re very protective of me.”

From navigating parenthood to becoming fashion trendsetters together, here’s everything to know about Paris Hilton’s relationship with her sister Nicky Hilton.

They have two other siblings

Barron, Kathy, Nicky, Paris and Rick Hilton in 2010. Fiona Hanson/PA Images via Getty Images

Paris and Nicky’s parents, Rick and Kathy Hilton, were married in 1979 and share four children together. In addition to their daughters, the couple share two younger sons, Barron Hilton, born in 1989, and Conrad Hughes Hilton, born in 1994.

Barron graduated from Loyola Marymount University in 2015 and has dabbled in acting, directing and producing. He married his wife Tessa Gräfin in 2018 and they share two children.

They are known for their fashion moments

Paris and Nicky Hilton in 2002.Djamilla Rosa Cochran/WireImage

In the early 2000s, Paris and Nicky emerged as fashion icons, though Nicky admits her older sister spearheaded the trends that, 20 years later, came back in full swing.

“I mean Paris started all the millennium trends and now there are still all of these girls dressing up like her,” Nicky told PEOPLE in 2019.

“Everyone thought I was crazy back in the day — wearing all these clothes — because nobody dressed like me,” Paris added. “Now I see on these runways – I go to my friends’ who are designers and on their mood boards there’s pictures of me from back in the day, it makes me feel really proud to see it all come to life. Very flattering.”

They may not be running around nightclubs anymore, but Paris and Nicky still have plenty of mood board-worthy fashion moments together. At Paris Fashion Week in the fall of 2023, the sister duo donned a series of matching Barbie-inspired looks while attending shows.

They admire each other

Paris and Nicky Hilton in 2020.Tibrina Hobson/WireImage

In a January 2021 TikTok livestream, Paris and Nicky opened up about their relationship and shared their favorite things about each other.

“You’re just fun as f—,” Nicky told Paris.

The sisters also divulged some of their pet peeves. Nicky claimed her sister is “always late,” while Paris said that Nicky “gets mad at me when I’m late … and she’s super bossy.”

They were each other’s maid of honors

Paris and Nicky Hilton at Paris’ 2021 wedding.Todd Williamson/Peacock/NBCU Photo Bank/Getty

Paris and Nicky were right by each other’s side on their wedding days.

In July 2015, Nicky married James Rothschild in London, with Paris serving as her maid of honor in a periwinkle chiffon gown.

At Paris’ November 2021 wedding to Carter Reum, Nicky returned the favor. She wore a baby pink Alice & Olivia gown that matched her fellow bridesmaids.

Paris stole her “that’s hot” catchphrase from Nicky

Paris and Nicky Hilton in 2023.Emma McIntyre/Getty

Paris became known for her signature catchphrase, “That’s hot,” in the early 2000s but in her 2023 book Paris: The Memoir, The Simple Life star admitted she first heard it from Nicky in middle school.

“At some point, I heard Nicky say ‘That’s hot,’ and it resonated with me,” Paris penned. “I wrote it in my diary and doodled flowers and fireworks around it. It’s such a great statement, isn’t it? Positive. Unpretentious. The word hot is evocative; there’s energy in it.”

She continued, “Suddenly there seemed to be a lot of things in my world that deserved this little accolade, and I recorded them faithfully in my diary,” she wrote. “Mom got me markers with glitter in them. That’s hot. We learned how to diagram sentences. That’s hot. Nicole [Richie] is sleeping over the whole weekend. That’s hot.”

Becoming moms has changed their bond

Nicky Hilton and her son Chasen; Paris Hilton and her son Phoenix.Nicky Hilton Instagram ; Paris Hilton Instagram

Nicky shared that since welcoming their children, she and her sister’s relationship has been different.

“I mean, usually around this time of the year we’re trying to figure out what we should do for New Year’s Eve, should we go to Vegas?” she told PEOPLE in December 2023. “But this year we’re talking about doing a trip with all the children.”

Nicky shares three kids — daughters Lily-Grace Victoria and Theodora “Teddy” Marilyn and her son Chasen — with Rothschild. Paris shares her two kids — son Phoenix and daughter London — with Reum.

To celebrate National Sons Day in September 2023, Nicky and Paris posed with their sons at the beach.

“Happy National Sons Day to our sons! 💙 Love doing this boy mom life with my bestie. 😊,” Nicky captioned the photo on Instagram.

Nicky defended Paris’ son Phoenix

Paris and Nicky Hilton in 2023.Victor Boyko/Getty

After sharing photos of her son Phoenix’s first trip to New York City in November 2023, Paris’ post was inundated with comments about the then 8-month-old’s head size.

“Living life in the spotlight, comments are inevitable, but targeting my child, or anyone else’s for that matter, is unacceptable,” Paris responded via Instagram Stories.

She continued, “This hurts my heart more deeply than words can describe. I’ve worked hard to cultivate an environment that is all about love, respect, and acceptance, and I expect the same in return.”

Shortly after, Nicky came to her nephew’s defense.

“I think that if you are bullying an infant then you have serious issues and you really [have to] take a look at yourself,” she told Page Six at the time. “It’s so demented.”

Their kids have playdates

Nicky and Paris Hilton with their sons in 2023.Nicky Hilton/Instagram

Though they live on opposite coasts (Nicky in New York City and Paris in Los Angeles), the sisters get their families together whenever possible.

In October 2023, Nicky told PEOPLE that while Paris was in town with her son, Phoenix, their kids were enjoying having playdates together.

“My sister is in town with her son Phoenix and it’s really cute,” Nicky said at the time. “My kids are having playdates with her kids every day after school. They don’t visit New York often so it’s fun to have all the cousins together.”

Paris would love to do a reality show about the Hilton family

Nicky and and Paris Hilton in 2023.Pierre Suu/Getty

Since The Simple Life, Paris has starred in other reality shows including her series Paris in Love, which debuted in 2021. Though Nicky has appeared on Paris in Love, she isn’t interested in a show of her own.

During a TikTok livestream in January 2021, the sisters addressed the idea of a reality series about the Hilton family. Paris was enthusiastic about it, but noted that her sister is “more shy.”

“Yes! I think our family is so much fun, so interesting … I think it’d be super fun,” Paris said. “Nicky is more shy than I am, but I would!”

They were once cast on Sex and the City

Paris and Nicky Hilton in 1999.Dan Callister/Online USA/Getty

Despite Nicky’s aversion to TV, the sisters revealed that in the 2000s, they were cast on Sex and the City — but never appeared on the show.

“It’s one of the true regrets ever,” Nicky told viewers during their January 2021 TikTok livestream. “Paris and I were cast as Samantha Jones’ new loud [and] rowdy neighbors in the Meatpacking District [of NYC].”

She explained that after attending Oscar night events in L.A., the sisters were “out late” and “did not get on the plane.” Nicky then shared that they were too “scared” to call the set so they “turned our phones off” instead.

“I’m very sorry Sarah Jessica Parker! I love you!” she added.