Time flies! The son of Tristan Thompson and Maralee Nichols celebrated his first birthday on December 1, surrounded by blue-and-white balloon decorations. The fitness model also wrote a lengthy letter alongside a few snaps of the pair.

“I can not believe you are already one. Spending the past 365 days with you have been the best days of my life,” she assured, adding that Theo is “the sweetest little boy,” and his smile “brightens up any room.”

“You are my greatest blessing, my world, my heart in human form,” she added. “God knew I needed you. I love you more than anything. Happy 1st Birthday to my angel, Theo.”

Although welcoming a child is a precious moment in one’s life, Tristan has reportedly made no effort to meet his third son. According to the birth certificate obtained by PEOPLE, Theo was born on December 1 in Santa Monica, California.

Tristan is not listed on the document since the birth was registered while Thompson was still disputing the child’s paternity. Nichols told the publication that the athlete’s “name was not on the birth certificate because he was not present at Theo’s birth.”

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Theo was conceived when Thompson and Khloé Kardashian were still together; the NBA player confirmed he was the child’s father in an Instagram Story. “Today, paternity test results reveal that I fathered a child with Maralee Nichols,” he wrote at the time. “I take full responsibility for my actions. Now that paternity has been established; I look forward to amicably raising our son.”