"We can't say the word happy but we'll say thank you for being a mother & giving me this sweet amazing boy," Dorsey, 37, captioned a Mother's Day tribute for Rivera on Instagram Sunday, along with a photo of the mother-son pair smiling together.
The father of one, 37, shares 5-year-old son Josey with the Glee star, whose body was found in Lake Piru in Ventura County, California, on July 13, 2020 — five days after she disappeared during a boat outing that she spent with Josey. The 33-year-old's cause of death was ruled as an accidental drowning and she was laid to rest on July 24.
In January, Dorsey penned a sweet message about his son on Instagram. "This little boy...man...I couldn't be any prouder of someone. At such a young age, he's endured more than anyone should at 5 years old," the dad wrote at the time.
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"Without even fully realizing it, he lives the #keeppounding mantra every day with his resilance [sic]," Ryan continued in his post. "You're so strong, so brave, and so kind. I will always be proud of you and we will always #keeppounding b/c that's all we can do."
Earlier that month, Dorsey shared a tribute on what would have been Rivera's 34th birthday. Dorsey and Rivera were married from 2014 to 2018 and welcomed Josey in September 2015.
"Just as surreal as it is real that you're gone. If that makes sense, but none of this still makes any sense..." he wrote on Instagram alongside a black-and-white photo of the family of three. "34..I could just hear you saying "Ah, I'm old AF now!" Ha...Rest easy old lady..."
Also on Sunday, Dorsey honored his own mother with a sweet photo of her and Josey. "Happy Mother's Day Grammy…Thanks for all the support, unconditional love, all the help, your patience, thoughtfulness, and everything you do. We ❤️you," the actor said.