"Auntie!" Teigen, 30, captioned the pic of Kardashian cooing to Luna, Teigen's daughter with husband John Legend, 37.
The supermodel also shared a cute video of West, 38, cradling the 6-week-old as his wife played with the little girl's tiny feet at Nobu Malibu.
The reality star, who has two children, North, 2, and Saint, 5 months, was a helpful friend to the first-time mom, offering advice on how to dress her baby bump and even taking Teigen and Legend out shopping for baby gear. (West and North took a nap in the Bel Bambini store while the others browsed.)
And in March, Kardashian, 35, threw a lavish baby shower at her home for Teigen, with a high-low theme that included McDonald's fries alongside extravagant decorations.
The new mom has been proudly showing off her adorable baby on Instagram and Snapchat. On Thursday, May 26, she shared a video on Instagram of Luna listening to one of her daddy's old songs, "The Beginning," which features the lyrics, "Soon as I saw you, baby, I had plans / Plans to do it 'til we have a baby / Even if the world is crazy / Pick some names, boy or girl / Then we'll change, change the world."
Want stories like these delivered straight to your inbox? Sign up now for the Us Weekly newsletter!