Ashlee Simpson and Pete Wentz's 13-Year-Old Son Bronx Is All Grown Up in Birthday Tribute

Growing up so fast!

Ashlee Simpson Ross and ex-husband Pete Wentz are now parents of a teenager! The duo’s son, Bronx, celebrated his 13th birthday over the weekend—and the “Pieces of Me” singer couldn’t help but gush over her son’s milestone.

“This is 13. Happy birthday Bronx!” Ashlee wrote in a Nov. 21 Instagram post. “You are the coolest teenager. I LOVE YOU. I LOVE YOU.” Next to the post was a black and white photo of Ashlee and her teen snuggled up on the couch, making for an extra sweet mother-son moment.

And Ashlee wasn’t the only one who celebrated the birthday boy. In fact, famous friends took to the comments to share their shock and blessings. “OMG 13,” Rachel Zoe wrote. Makeup artist Mary Phillips added, “Stop!!! Omg it feels like yesterday he was in your belly.” 

Bronx’s stepdad, Evan Ross also got in on the celebration.