Cassandra, 35, is Caitlyn's daughter from her first marriage to Chrystie Crownover -- and has admitted to growing closer to Caitlyn since her transition.
"My relationship with Caitlyn is much better than with Bruce, but we still have a lot of work to do," she told People last year. "We didn't talk for years, and now we see each other every couple of weeks and talk on the phone, which I am grateful for."
"She's happier and more appreciative of her family," she added. "She is trying harder, and there is a softness to Caitlyn that is new to me. I think part of that is that when someone is happier, they are just nicer."
Cassandra's newborn son is the second Jenner grandson to be born this year. Her brother Burt, 37, welcomed a baby boy named Bodhi in July.