Naomi Watts is celebrating a milestone moment for her son Sasha Schreiber.

The 21 Grams actress commemorated Sasha’s 18th birthday by sharing some rare photos of herself with her son, who she shares with ex Liev Schreiber.

“Happy birthday sweet, darling @sashapeteschreiber,” Naomi captioned her July 25 Instagram carousel post. “18 today-and ready for the world! Cannot believe it.”

“Have so loved watching you grow into the kindest, most wonderful young man,” she added. “Thank you for making me a first time mum.”

The 56-year-old—also mom to daughter Kai Schreiber, 16, with Liev—posted a solo shot of Sasha looking all grown up, in addition to three photos of them together, including one of Naomi holding her son as a baby and two more recent photos of them smiling with one another.

Sasha’s 18th birthday comes just over a month after Liev and Naomi—who split in 2016 after 11 years together—reunited to celebrate his high school graduation alongside their current spouses Taylor Neisen and Billy Crudup, respectively.