"Your sister is soo lucky to have a big brother like you to watch and protect her," Thompson wrote, referencing 2½-year-old daughter True

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Tristan Thompson and son
Tristan Thompson and son Prince
| Credit: Tristan Thompson/Instagram

Tristan Thompson is showering Prince Oliver with love!

The Boston Celtics player, 29, shared a birthday sweet tribute on Saturday to his 4-year-old son with ex Jordan Craig.

Happy birthday Princey!!!” he wrote alongside two adorable images, one of which showed the father-son pair making silly faces together. “I’m soo lucky to have you as a son.”

“Your heart and soul is pure gold. Your sister is soo lucky to have a big brother like you to watch and protect her,” he added, referencing 2½-year-old daughter True, whom he shares with girlfriend Khloé Kardashian.

Continuing, he added, “Daddy Loves you baby boy ❤️🙏🏾💪🏾🤘🏾❤️.”

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Tristan Thompson and son
Tristan Thompson and son Prince
| Credit: Tristan Thompson/Instagram
Tristan Thompson and son
Tristan Thompson's son Prince
| Credit: Tristan Thompson/Instagram

In her own social media post, Craig called Prince “the most BRILLIANT, Loving & Kind son a Mum could ever ask for.”

“Here’s to another year & many more to come!” she added alongside a slideshow of images documenting a snow-filled sleigh ride the pair took together in honor of his special day.

RELATED VIDEO: Khloé Kardashian Brings Daughter True, 2, While Donating Toys to 'See How We Give Back to Others'

Thompson and Kardashian, 36, officially got back together over the summer, after their relationship was on the rocks for some time due to his past cheating scandals.

"Their focus is True and they keep doing fun family activities together. Khloé really believes that things will continue to be great even after Tristan has to return to work," an insider told PEOPLE at the time. "She is very impressed with how he has stepped up."

True Thompson, Khloe Kardashian, Tristan Thompson
Tristan Thompson and daughter True
| Credit: Khloe Kardashian/Instagram
Tristan Thompson and Khloe Kardashian
Tristan Thompson and Khloé Kardashian with daughter True
| Credit: Tristan Thompson/Instagram

The pair have kept their relationship mostly under wraps since getting back together, though they did dress up as a family this past Halloween.

Last month, Thompson signed a $19 million deal with the Boston Celtics for two years after playing for the Cleveland Cavaliers for nine seasons.

Just days later, the reality star shared a slew of cryptic messages about not caring what others think. "Your life isn't yours if you always care what others think," read one post, while another read, "If it makes you happy it doesn't have to make sense to others.”