Nicky Hilton is 40! Sister of Paris Hilton, 42, celebrates milestone in elegant fashion in Paris… almost 20 years after her wild youth

Nicky Hilton turned 40 on Thursday.

It is an important milestone for the younger sister of 42-year-old pin-up Paris Hilton.

The New York City native celebrated with a party in Paris when she posted the fun images to Instagram after attending several fashion shows with her older sibling.

The 365 Style author was seen wearing a black sparkly mini dress with her hair pulled back as she sat on a glass-topped coffee table next to several birthday cakes.

‘I couldn’t have asked for a better birthday week in the nicest city with my best friend! Most epic sister’s trip! ❤️” she said of spending time with Paris in France.

The star – born Nicholai Olivia – is the wife of James Rothschild of the famous Rothschild family.

He is a grandson of Victor Rothschild, 3rd Baron Rothschild.

In May, Nicky, mother of three children, opened up E! News on advice she gave to her sister Paris, who welcomed her first child via a surrogate mother.

‘My advice is always: don’t miss the little moments. There’s such a short window of time that they’re so small, and new things are happening every day,” Nicky said.

“For example, Paris always says her son looks different every day,” Nicky said, adding, “She’s so happy. She’s so happy.’

“I was there last week and just hanging out in the nursery with her and her son, and she’s so complete, that’s the word I would use,” she continued.

Party people: at the Stella McCartney show during Paris Fashion Week Womenswear Spring/Summer 2024 in Paris in October

Q: At the Valentino Womenswear Spring/Summer 2024 show as part of Paris Fashion Week on October 1 in Paris

Nicky added that Paris’ son Phoenix “looks a lot like me as a baby, and my daughter Lily-Grace looks identical to Paris as a child.”

“So it’s interesting how the genes crossed like that,” she said, adding how interesting it is that she grew up in a family made up of mostly girls, while she, her sister and brother Barron all had boys.

“Funny, we all had girls in the family and this past year my brother had a son, Paris had a son and I had a son,” Nicky said.

“So we’re inundated with guys, and it’s great to see the bond between them,” she added.

Happy gal: She was also spotted at the Plaza hotel on Thursday with a croissant in hand