Ashlee Simpson's Son Bronx Stands Almost a Head Taller Than Her in Sweet Mother-Son Photo: 'Beautiful Night'

The singer shares Bronx with ex Pete Wentz and is also mom to daughter Jagger, 8, and son Ziggy, 3, with husband Evan Ross

Ashlee Simpson Ross' son Bronx looks all grown up!

Over the weekend, the singer, 39, shared a Reel on her Instagram from mother-in-law Diana Ross' birthday party, posing with husband Evan Ross, 35, and her son Bronx, 15, whom she shares with ex Pete Wentz, 44.

In the sweet mother-son photo, Bronx stands almost a head taller than his mom, matching her white fuzzy dress with an all-white suit.

"Thank you for this fabulous look. Such a beautiful night of love and celebration with family and friends. Happy birthday mama d ??," Simpson Ross wrote in her caption.

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Related: Ashlee Simpson Dances with Daughter Jagger in Cute Home Video: 'Boogie Down with the Queen'

Simpson Ross is also mom to daughter Jagger, 8, and son Ziggy, 3, whom she shares with husband Evan.

In August, the proud mom shared a photo of her family at daughter Jagger's 8th birthday on herInstagram, which included a rare photo of Simpson Ross' son Bronx. In the family picture, Bronx towered over his mom as they posed together for the camera.

Earlier this year, Simpson Ross chatted with Jennifer Hudson on her talk show about her son Bronx, sharing that he'd been growing up so quickly. The "Pieces of Me" singer added that she was shocked at how her oldest is "so tall."

"He's like 5' 9?", he towers over me," said Simpson Ross. "He's really chill, though, so I'm lucky for that." She also noted that Bronx's "voice is deep, he's a young man."

She also opened up about a recent mishap that happened when she went out to dinner with her son and husband. "I'm sitting next to Bronx and Evan is on [the other] side, and we're at one of those movies where they offer you wine or something, and they were like, 'Oh sir [to Bronx], would you like something?'"

Simpson Ross quickly moved to correct the waiter, saying, "He's not my friend — well he's my friend, but this is my kid, my 14-year-old son."

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