"I know he is watching over me and my family though from all of the amazing signs he has given us. Love and miss you so much, Mikey," she added.
Michael was discovered dead at age 30 on Dec. 10, 2015, after being reported missing a few days previous. Cavallari had given birth to daughter Saylor the month before, and told People in October that her brother's death brought her closer to her family.
"I've been kind of emotional about it [lately]," she told the magazine. "Anytime you lose somebody, obviously it makes you appreciate everyone you have in your life."
"I definitely have been closer with my parents and my entire family in general," the star added. "It makes you appreciate everyone you have."
Cavallari previously told "Entertainment Tonight" that she "found a lot of strength in [her] kids" after her brother's passing.
She shares 1-year-old Saylor, 2-year-old Jax and 4-year-old Camden with husband Jay Cutler.
"I had Saylor at the same time my brother went missing and ultimately passed away," the star said in March.
"I couldn't collapse. I had a newborn baby to look after. I had to be strong for her and for my whole family. So that's what I've been doing."
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