Jack, her third child with her husband, singer John Legend, passed away before his birth and the couple shared personal photos in the hospital following their loss.
Teigen penned a personal essay about their grief and on Monday she posted a video of their 4-year-old daughter, Luna, with the box containing Jack's ashes.
"im just thinking a lot about jack today," the caption read. "our house is very open about life, death, grief, everything really. we try to explain things well and answer every question imaginable in a beautiful, spiritual but literal way."
In the video Jack's ashes are seen in a box tied with some "blessed, holy Thai string," in honor of Teigen's heritage.
She said Luna had placed a therapy bear and a piece of her favorite snack, Pirate's Booty, with her brother's ashes.
"This is the cutest, most beautiful thing I have ever seen," Teigen said.
In the video featuring Luna the youngster can be heard saying, "Hi guys. Hi this is baby Jack and I'm Teddy. I'm Luna. How are you doing today?"
Teigen said it was "a weird post" while adding, "I just wanted to share these to always remember my incredibly empathetic little mini," referencing Luna.
"life is infinitely better with her in it," Teigen wrote. "I miss u, jack. we miss you a lot."
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