Paris Hilton Reveals Mom Kathy Hilton Didn't Know About Son Phoenix Until He Was 'Over a Week Old'

Paris Hilton's immediate family didn't know about her baby boy, Phoenix Barron, until a week after his birth

Paris Hilton is opening up about her decision to share her baby news on her time.

On her iHeartRadio podcast This Is Paris, the new mom, 42, talked about how she and husband Carter Reum decided on "keeping everything really private."

"Not even my mom, my sisters, my best friend knew until he was over a week old," Hilton revealed on the podcast. "It was really nice to have that with Carter, be our own journey together. I just feel like my life has been so public, and I've never really had anything be just mine."

The "Stars Are Blind" singer talked about how her life in the public eye has been "invaded" many times, while the entrepreneur, 42 — who is already a dad to a daughter whom he shares with former reality star Laura Bellizzi — "has always been a really private person."

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"So when we were talking about it, I really felt that I wanted this journey to be for us only," Hilton explained, noting it was "hard to keep that in."

Paris Hilton and Kathy Hilton. Charles Sykes/Bravo/Getty

"Because we were so excited and wanted to tell our families, but we were just nervous because if you tell a person, then they tell someone, and all the sudden, it's in TMZ or Page Six, and I've had enough of my life like that," she continued. "So Carter and I literally made a pact together that we would not tell anyone, and no one knew until just recently."

That decision meant that Paris' mom, Kathy Hilton, didn't meet grandson Phoenix Barron until he was about a week old.

Jeff Kravitz/FilmMagic

"When I introduced my mom to our baby boy, it was amazing to see the look on her face," Paris shared. "She was so surprised — just the look on her face, it was priceless."

Celebrating her baby boy's arrival after revealing his name for the first time, Paris added, "We are just so happy and feel so blessed. He is so perfect, and it's amazing being a mom."

The Real Housewives of Beverly Hills star, 63, told PEOPLE exclusively that she and husband Rick Hilton "are over the moon" after the birth of their latest grandson.

"Paris and Carter, we know you are going to be the most amazing parents," Kathy said in a statement to PEOPLE. "We are so thrilled for you both! Thank you for this perfect addition to our ever-growing, beautiful family."