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Bristol Palin celebrates brother Trig on World Down Syndrome Day: He's 'perfection'

/ Source: TODAY

Tuesday was World Down Syndrome Day and Bristol Palin marked the occasion with a tribute to one of her very favorite tykes — her younger brother, Trig.

Palin shared a smiling shot of the 8-year-old on Instagram and penned an equally sweet message for the little guy she calls the "the boss."

"Trig continues to light up our world!!" she cheered. "He IS the boss around here and continues to fill our days with so much laughter! He is stubborn, and knows exactly what he wants - right this second. He's got everyone wrapped around his short chubby fingers - especially my dad who constantly stops by his school to make sure that he ate his lunch, and that his face is clean."

The former "Dancing With the Stars" alum also stressed just how thankful she and the rest of the family are to have Trig in their lives.

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"Trig is our definition of perfection," she wrote, "and there isn't one day that goes by without us feeling so thankful that God chose us to be his family."

And the 26-year-old's family is still growing.

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Palin — who has an 8-year-old son, Tripp, with ex-fiancé Levi Johnston and a 1-year-old daughter, Sailor, with husband Dakota Meyer — is currently 8 months pregnant with her third child.