The "Lost Without U" musician, 45, shared a heartfelt post to Instagram on Friday, commemorating the Growing Pains actor, who died nearly six years ago in December 2016.
"Missing my Pops today," Robin captioned a photo. "Mr cool 😎"
The image shows a young Robin with a backwards cap as he and his father — decked out in shades — sitting on a boat and staring off into the distance. The father-son duo sit close to each other in the shot, which looks to be a print from a disposable camera.
It's been nearly six years since Thicke tragically died at age 69 shortly after playing hockey with his youngest son, Carter. The longtime actor's cause of death was eventually revealed to be a "ruptured aorta" and a "standard type A aortic dissection," according to his official death certificate obtained by PEOPLE.
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In 2019, Robin spoke candidly about his having matured and embracing his role as family patriarch in an interview with Steve Harvey. At the time, he said he had a "little maturing to do" when his father died. Thicke also explained that he eventually realized he had to step up for his half-brother Carter, who was 19 at the time of Alan's death.
"When my father passed, I became the patriarch of my family. My young 20-year-old brother, he needed a big brother, and it just felt like now I had to take it onto my shoulders to be a much better, more focused, man than I was before," Robin explained.
Charley Gallay/Wireimsage Alan and Robin Thicke in 2013
Throughout the tribute, sitcom-style throwback photos of Robin and fellow Masked Singer judges Ken Jeong, Jenny McCarthy and Nicole Scherzinger and host Nick Cannon appeared on screen, as Cannon asked the audience to cheer for the "unforgettable" Alan.
Just a year before, Robin opened up to PEOPLE about the meaning behind the track "That's What Love Can Do," the first song he wrote after his father's death.
"It's about the passing of the torch of my father to me and the kind of man I want to be," he said. "After my father's death, I remember a friend of his said, 'A big tree has fallen.' That's what my dad was: the big tree. Now here I am, this medium-size tree, and I've got to grow my branches and protect everybody. Every day I try to make him proud of me."
"I was suffering blow after blow, loss after loss," Thicke added. "But I saw the house burning down as a chance for me to step up and say, 'We're going to laugh today. We're going to smile today. We're going to play today. We're going to dance. We're not going to let losing our stuff matter because we've got each other.' Loss does beget gratitude."