Fergie knows big girls don’t cry, but she just can’t help it.

Indeed, the Grammy winner got emotional as she and her ex-husband Josh Duhamel celebrated their son Axl’s 13th birthday, marking the milestone by sharing rare snaps of their not-so-little guy. 

“13. Wow, my teenager,” Fergie wrote on Instagram Aug. 29 alongside never-before-seen photos of Axl. “I’m saying that with tears in my eyes as I feel like the world is shifting beneath us. It’s so beautiful to watch you grow into the kind, silly, and cool dude you are. You are so tough bruh.”

“Happy 13th Axl Jack,” she added. “I love you.”

In one snap, Axl—dressed in a black graphic T-shirt and white pants—gives the camera his best serious face as he poses against a wall with his blonde locks falling over his face. Meanwhile, another pic proves the teen is the same height as the Black Eyed Peas alum as the pair smile in coordinating black outfits.

Fergie, 51, also shared a few throwback pics of Axl, including one where she holds her then-baby boy on her hip and another of him playing in a ball pit as a toddler.