Caitlyn Jenner has a new grandchild in her life!
The star, 68, celebrated the arrival of daughter Kylie Jenner‘s baby girl on Instagram Monday with a throwback photo of the Keeping Up with the Kardashians reality star, 20, when she was just an infant.
“My daughter just had a daughter. It’s amazing to be by your side through this journey. She’s SO beautiful already. Can’t wait to watch her grow. Throwback to my baby, as a baby @kyliejenner,” Jenner captioned the picture.
The new mom, who welcomed her first child with rapper boyfriend Travis Scott on Feb. 1, expressed thanks for the sweet message by commenting, “Love you.”
Though Kylie has yet to share a photo of the newborn, a source told PEOPLE Monday that the baby “is very cute with chubby cheeks.”
Caitlyn’s Instagram post follows congratulatory messages shared by Kylie’s sisters on Sunday, the same day the Lip Kit entrepreneur announced her baby’s arrival.