"It's like a relationship was ripped out of my arms," says Lisa Vanderpump, on her brother's death

It’s been a year and a half since the tragic death of Lisa Vanderpump’s older brother, and the former Real Housewives of Beverly Hills star is still reeling from the shock.

“To lose my brother unexpectedly with no closure or conversation is like a relationship ripped out of your arms,” Vanderpump, 59, tells PEOPLE about her only brother. “Grieving takes time.”

Mark Vanderpump died by suicide in April 2018 following a battle with depression. “I never thought suicide would touch my life,” says Vanderpump, who also works with The Trevor Project, a non-profit focused on suicide prevention among LGBTQ youth. “For the people left behind there are so many unanswered questions and feelings like, ‘Could I have done this? Should I have done that?’ It’s very difficult to deal with.”

Her immense sorrow ultimately led to a fateful decision to leave Housewives after nine seasons.

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lisa vanderpump and brother at table
Credit: Lisa Vanderpump/instagram

“I started to realize the fragility of life and what I wanted to achieve while I’m still here,” says Vanderpump, who, in addition to her restaurants and the Bravo hit series Vanderpump Rules, co-founded Vanderpump Dog Foundation, which will hold its annual gala on Nov. 21 in L.A. “Everything shifted in my brain. I needed the support of friends. And I didn’t have room in my life for negativity.”

Vanderpump was surprised by the enormity of her grief.

“I was in a very dark place,” she reveals. “I was crying every single day. And I spent months just staring at the walls.”

Lisa Vanderpump
Credit: Tibrina Hobson/Getty Images

Support came in the form of Ken Todd, Vanderpump’s husband of 37 years, who was first introduced to her by Mark.

“Ken was as devastated as I was about my brother,” says Vanderpump. “He loved him.”

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Now, Vanderpump is focused on her future — and on keeping the memory of her brother close.

“You pass those hurdles like the first Christmas they’re not here or the first birthday, and then realization sinks in that you’re never going to see them again,” she says. “It’s been hard to deal with, but I’m a very buoyant person. Even in the depths of grief I try to see the bright side.”

The Vanderpump Dog Foundation’s annual gala will take place Nov. 21 in Los Angeles. Click here for tickets.