Ashlee Simpson's son with ex Pete Wentz is so much taller than her in rare new photo

Ashlee Simpson Ross already has a teenager in her household, and he sure looks it, with the height to prove it!

The singer's eldest son, Bronx, who she shares with ex-husband Pete Wentz, is already a year into the angsty teenage years, and will celebrate his 15th birthday later this year.

In a new photo shared by his mom, her fans were left shocked at how grown up he looks already, and stands taller not only than his mom, but also his stepdad, Diana Ross' son Evan Ross.

Ashlee took to Instagram to share a glimpse into her middle daughter Jagger's birthday celebrations, unsurprisingly defined by the theme of the summer: the now-ubiquitous Barbie trend.

However, while it was little Jagger celebrating her seventh birthday, and she sure seems to have had a blast, it was her older brother's height that took up a lot of the attention.

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In the first photo Ashlee shared, the family-of-give is posing together next to a hot pink balloon arrangement, and Bronx, who is standing next to his mom, is totally towering over her.

"How is your son this old!!!! Time is a thief!" one fan couldn't help but ask in the comments section under the post, as others reiterated the sentiment with: "Omg Bronx is so tall!" among plenty more praise for the sweet family portrait.

MORE: Ashlee Simpson shares adorable photo of daughter Jagger Snow

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Ashlee and her ex-husband Pete welcomed Bronx, middle name Mowgli, in 2008, the same year they tied the knot.

The two split in 2011, and Ashlee married Evan in 2014, while the Fall Out Boy rocker shares son Saint, nine, and daughter Marvel, five, with longtime partner Meagan Camper.

"He's like 5' 9½", he towers over me… [his] voice is deep, he's a young man" Ashlee told Jennifer Hudson during a recent appearance on her talk show, and that: "He's really chill, though, so I'm lucky for that.

"It's great. We have a great family," she also told Us Weekly about her blended family, adding: "We really lucked out."

MORE: Evan Ross shares unseen photos from fairytale wedding to Ashlee Simpson

Her husband also told the outlet: "I think the fact that there is a lot of respect amongst all of us. That makes it easier," and that: "It's easy, we got really lucky with that."

Plus, he gushed about his stepson: "[He] is brilliant. I think he's, like, about to be the next George Lucas [with] his imagination."

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