Caitlyn Jenner's daughter has given birth to a baby boy

In one post, the 36-year-old beauty wrote: "He made it! One day before his due date and on Mike's dad's birthday. 8lb 13oz 22 inches long. I am elated and exhausted but a super happy non-pregnant mama :). (sic)"

She also posted another photo of her two daughters Isabella and Francesca getting a first look at their new baby brother, whose name has not yet been announced.

The photo was captioned: "Proud big sisters. They are over the MOON (sic)"

Cassandra - who is Caitlyn's daughter from her first marriage to Chrystie Crownover - previously admitted she's grown closer to Caitlyn since her transition last year.

She said: "My relationship with Caitlyn is much better than with Bruce, but we still have a lot of work to do. 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 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."

For Caitlyn, 66, the birth of Cassandra's son marks the second of her grandchildren to be born this year after 37-year-old Burt - who she also has from her marriage to Chrystie - welcomed a baby boy named Bodhi is July.