They just finished celebrating their successful adoption of Robyn's kids, but the Brown family will be in for a major shock and drama on Sister Wives.  

The Brown Family's Adoption Party Plan Go Awry

In a preview clip for the upcoming episode, the family's celebration is set to initially continue with a trip to Alaska, where they not only continue being happy about Dayton, Breanna and Aurora being adopted, but also decide to learn whether or not baby no. 18 will be a boy or a girl.

"We're doing this ultrasound to find out the sex of the baby so we can tell everyone in Alaska," Kody says excitedly in the clip.

Are Robyn & Meri Faking Friendship?

However, the celebration will be cut short-and potentially destroyed, when Meri decides to inform Kody, Robyn, Christine and Janelle about a huge secret in her life-one which threatens to destroy the family completely.

"So, I guess I should bring something up," she says to everyone at a dinner. "It's no surprise that I've been struggling with stuff."

And though she knows she needs to tell them the truth, it will be difficult for Meri to admit to what happened, and how much it will hurt everyone else.

"It's never easy when I need to talk to the family and I feel like there's something that I need to bring up," she says. "They have no idea how bad it is. They don't know what I've brought into the family."

Sister Wives airs Sundays at 9 p.m. on TLC.

Tags: Sister Wives TLC Reality TV