The Kardashian-Jenner family is celebrating its late matriarch, Mary Jo -- known as MJ -- on what would have been her 92nd birthday.

Kris Jenner marked her late mother's birthday Sunday with an Instagram carousel filled with family photos from over the years, writing ... "Happy Heavenly Birthday Mommy. I love you."

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Meanwhile, Kim Kardashian also shared her own collection of memories with MJ, revealing she and Kris have been going through her grandmother's belongings since her death -- and learning there was still plenty they didn’t know about her.

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Kim wrote the discoveries have made her respect and love MJ even more, adding ... "Today we celebrate you! I miss you like crazy and I love you endlessly my sweet grandma MJ."

As we reported ... Kris announced her mother's death July 16, remembering MJ as the heart of their family and crediting her with teaching them to love fiercely, show up for one another and cherish every moment.

Kim also mourned MJ in an emotional tribute at the time ... calling her grandmother her "best friend," "gossip buddy," and "forever twin."

The family has not shared MJ's cause of death or any additional details surrounding her passing.

Happy heavenly birthday, MJ!