Haylie Duff Gathers a Slew of Brady Bunch Stars in PEOPLE Presents: Blending Christmas Trailer

Here's the story of a lovely lady... who thought she was going to spend the holidays with her boyfriend at her favorite resort.

In the exclusive trailer for the new Lifetime Christmas movie, PEOPLE Presents: Blending Christmas, we get a taste of the chaos that ensues when that lady, Emma (Haylie Duff), and her man, Liam (Aaron O'Connell), bring their families together.

As the voiceover teases, "Will this romantic holiday getaway be ruined by a Bunch... of unexpected guests?"

Liam brings Emma to dinner for a big surprise: Her big, loud family, and his as well.

Those family members are played by none other than original Brady Bunch stars Barry Williams, Christopher Knight, Mike Lookinland, Susan Olsen and Robbie Rist, as well as Brady Bunch movie star Jennifer Elise Cox, Beth Broderick, Telma Hopkins and Greg Evigan.

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But bringing their families to the resort isn't Liam's only surprise this Christmas. He's also planning to propose!

Not surprisingly, everyone in both families has their ideas for how that should happen, and soon, they're bickering over the details.

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All the drama may lead Liam and Emma to question their relationship altogether. Will this group still be able to somehow form a family?

PEOPLE Presents: Blending Christmas, which is directed by Marla Sokoloff, premieres Dec. 12 at 8 p.m. ET/PT on Lifetime.