Bruce Willis and Demi Moore are set to become grandparents.

Their 34-year-old actress daughter Rumer and her partner Derek Richard Thomas took to Instagram to share a series of black-and-white snaps of her blossoming bump on Tuesday (20.12.22) and simply captioned the post with a seedling emoji.

Vista Kicks frontman Derek can be seen tenderly kissing the bump in one shot.

Demi, 60, re-posted the pictures to her own page and declared: “Entering my hot kooky unhinged grandma era."

To which Rumer replied: “Love you mama.”

Rumer and Derek confirmed their relationship in November.

The musician captioned a series of pictures on a snowy woodland dog walk with the 'House Bunny': “In the short time we’ve been together you have filled my life with joy and peace."

He gushed: “Everything is just so easy with you. We sing, we dance, we play and most of all we laugh. Thank you for being you you’re a magical human I’m so glad you came into my life."

It's not known exactly how long they've been dating but in May, she hailed Derek one of “the most talented singers and songwriters I have heard in a very long time (maybe ever).”

Just recently, 'Ghost' star Demi shared a festive snap of their blended family.

Bruce and his wife Emily Heming-Willis and their daughters Mabel, 10, and Evelyn, eight, were joined by Demi and her kids with the action star Rumer, Scout, 31, and Tallulah, 28, in the holiday portrait.

Bruce retired from acting earlier this year, at the age of 67, due to his aphasia diagnosis, a cognitive condition that impacts a person's ability to speak, write and understand language, both verbal and written.

In the summer, Derek had an impromptu jam session with music-lover Bruce.

In the heartwarming social media clip, the 'Die Hard' star sat at the bottom of the stairs playing the harmonica while the indie rocker sang and played guitar.

Emma captioned the post: "Their talent is speaking for itself. I’ll just leave this here."

She added on her Instagram Story: "Impromptu jam session with @derikrichardthomas."