Heather Dubrow's Daughter Kat, 15, Comes Out as a Lesbian — 2 Years After Sister Max Came Out as Bi

Heather Dubrow and her family are getting ready to share their family's story with the world.

One year after her eldest daughter Max, 18, came out as bi, her second daughter Kat, 15, has news to share as well: she's a lesbian.

"We've got four kids, they are different genders, different sexualities, and all at interesting places in their lives, figuring out who they are and where they belong as humans," says Heather, 53, who is mom to son Nick and his twin sister Max as well as Kat, and Coco, 11.

A desire to share their family's story — and use their platform for good — factored in to their decision to return to Real Housewives of Orange County this season. "I felt like our purpose is to keep those conversations going in other families," says Heather.

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Adds her husband, renowned plastic surgeon and the star of Botched, Terry Dubrow, 63, "Coming out with your sexuality is something that broadly affects a lot of different people. We just want people to realize it should be part of normal conversations."

That's how it's been in their own home.

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"I was raised by 1950s parents. They talked about nothing. I had no idea," says Heather, who also hosts the podcast, Heather Dubrow's World. "These kids, they talk about everything and I think it's so, so important."

After Max came out privately to her mom at the beginning of the pandemic, "I guess I didn't make a big deal about it," she recalls. "She texted me and goes, 'I've got to tell you something.' I'm like, 'What?' She's like, 'I'm bisexual.' I'm like, 'Yeah. I know. Remember we talked about it?' "

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RELATED: Heather Dubrow on Supporting Daughter Max When She Came Out at 17: 'Nothing She Could Tell Me Would Upset Me'

A year later, their second daughter "had been talking about her sexuality for a while," Heather recalls. But when it came to breaking her big news to the family, she was very low key.

One day, "Kat decided to drop in our family group text, 'By the way, I'm a lesbian,' " Heather recalls. "I didn't see it, and I was mad because the dogs pooped in the house, so I wrote back, 'Who let the dogs poop in the house?' It was a total mom fail, and they've never let me forget that."

"All I cared about was creating an environment where they all felt safe, comfortable, happy," says Heather.

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The kids themselves say the live-and-let-live vibe in their home has made a huge difference in feeling at ease as they explore their identities.

"Even if she doesn't understand something, my mom tries very hard and she learns and teaches herself and she grows with us," says Max.

Adds Kat: "She's asked me trillions of questions that really show she cares. She's asked me about my pronouns. It's really easy to talk to her. It's not like I have to build up courage if I have something to tell her."

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While Kat has been out to her family for nearly a year, an episode of Housewives airing later this month shows her opening up about her sexual identity, and she's having mixed feelings about being so public.

"I was really stressed about it," Kat admits. "But I'm really grateful that I have Max as an older sister, that she has already gone through all of this. Seeing my sister be so proud, and to see her be so comfortable with herself, it just makes me feel like I have nothing to worry about."

The family has some fears as well. "Even though our family is very inclusive and accepting, of course you worry about what people going to be like out in the world. And on social media," Heather says.

Adds Max, who launched a podcast and wrote a guidebook for parents looking to support their LGBTQ+ children, I'll Give It to You Straight-ish, in 2021: "It's hard. Being unapologetically your- self, you just have to not care because it doesn't matter what anyone else thinks. But that's much easier said than done."

But Heather is confident in her girls' inner strength.

"These guys grew up with social media. They're better at filtering [negative] comments than adults are," she says. "They're all solid kids and they have each other's back. Even if they're bickering, they protect each other. They always take care of each other."

for more from Heather Dubrow and her family, pick up the latest issue of PEOPLE, on newsstands Friday.