"I can't wait to have my own little baby girl that you will best friends [with] just like your mom & I!" Paris Hilton addressed Lily-Grace on her birthday

Happy birthday, Lily-Grace Victoria!

Sunday marked two trips around the sun for Nicky Hilton Rothschild‘s older daughter, who received a heartfelt message from her aunt Paris Hilton to mark the occasion.

“Happy Birthday to my beautiful niece Lily-Grace! 🎉👶🏼🎂🎉 I am so in love with you my precious little angel! 👼🏼 You have brought so much love & happiness into of my life!😍,” Hilton wrote alongside a photo gallery featuring Lily-Grace with her mom and aunt.

The 37-year-old heiress also hinted at her hopes for her own family expansion, adding, “I can’t wait to have my own little baby girl that you will best friends [with] just like your mom & I! Love always #AuntParis

Want all the latest pregnancy and birth announcements, plus celebrity mom blogs? Click here to get those and more in the PEOPLE Babies newsletter.

Credit: Paris Hilton/Instagram

Lily-Grace Rothschild

Credit: Paris Hilton/Instagram

Lily-Grace Rothschild

In January, Hilton’s rep confirmed to PEOPLE that her boyfriend Chris Zylka had popped the question with a 20-carat pear-shaped diamond ring during a ski trip in Aspen, Colorado.

“I think Lily-Grace definitely will be [a flower girl],” Hilton Rothschild, 34, told PEOPLE in March of her sister’s wedding, adding of her then-11-week-old younger daughter Theodora “Teddy” Marilyn, “I don’t think Teddy will be walking yet.”

“Lily-Grace gets excited when Aunt Paris comes over because she loves animals and Paris always has her dogs with her,” she added, explaining that the proud aunt flew in for Teddy’s December birth. “Every time Paris is in New York, she makes a point to come visit the girls every day. It’s very sweet.”

The Colleagues And Oscar de la Renta's Annual Spring Luncheon
Credit: Jon Kopaloff/Getty Images

Paris and Nicky Hilton

RELATED VIDEO: Nicky Hilton Rothschild Wears Matching Ensembles with Her “Little Mini Me” Lily-Grace

And while Hilton may be busy planning her wedding with Zylka, 33, she’s definitely already got babies on the brain. As she told PEOPLE in April, “I loved growing up in a big family with four kids, with two brothers and a sister.”

“I want at least two [kids],” she revealed, adding that she would “definitely want a girl first.”

Hilton Rothschild told PEOPLE at the event, “Paris is like a big kid. So, I think she’ll be an amazing mom. She’ll just do so many fun things with her kids.”