Gwyneth Paltrow can't believe her son is 15: 'Holy Moses'

Time flies, and nobody seems to know that better today than Gwyneth Paltrow, who can't quite fathom that her little boy is 15.

She said as much in a post on Instagram featuring two pictures of her teenage son, Moses, whose dad is her ex-husband, Chris Martin.

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"Holy Moses I can't believe you are 15 today," the proud mom wrote in the caption. "You are the dreamiest, sweetest, most brilliant guy ever. I love you so much, you can't fathom it. Happy birthday you little shredder."

The first picture is a close-up of Moses, looking tousled and handsome; the next image explains the "shredder" comment, as he's seen executing a slick move on a skateboard.

Paltrow's children have grown up mostly out of the spotlight, except for a few appearances with their famous parents onstage and off, and occasionally on social media.Last Thanksgiving Day, the Goop founder shared an Instagram picture of herself with Moses and his older sister Apple, 16.

For his 14th birthday, Paltrow shared another loving tribute to Moses, calling him "immensely talented and a great friend," and last June, the young man showed he had one more talent in his back pocket: crashing his mother's interview on "The Tonight Show."

"Oh my god, look at this. Look who just popped in," Paltrow told host Jimmy Fallon when Moses showed up. "Look at how big he is."

Fallon asked him how he was doing and the kid was nothing but polite: "I'm good, thank you. How are you?"

Clearly, he's growing up quite well ... and super fast. Holy Moses, indeed!

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