'Selling Sunset' Star Dog Dies, Jason Oppenheim & Mary Fitzgerald Mourn Loss

The "Selling Sunset" family has lost a beloved furry family member!

Co-stars Jason Oppenheimand Mary Fitzgerald announced the devastating passing of their dog, Niko, who was a constant presence in the hit Netflix reality show.

Oppenheim and Fitzgerald took to Instagram to break the news of Niko's passing in a heartfelt statement. Alongside several photos of the proud fur parents with their pets, including one of a joint tattoo of his name, the heartbroken pair penned:

"With the heaviest hearts we write this letter to you our sweet baby boy, for 18 years you made us smile and laugh, and filled our world with immeasurable happiness."

The tribute continued, "With your unconditional love and loyalty, you comforted us when we cried and helped heal our hearts when they were broken. You lifted us in times of need and celebrated with us our wins and successes."

Oppenheim and Fitzgerald appreciated their late dog for the "valuable lessons" he taught them, adding that the beloved pet "opened our eyes to depths we had no idea love can reach, taught us a higher level of patience and selflessness, and showed us what true loyalty and devotion looks like."

The "Selling Sunset" stars praised late Niko for being "a patient, protective, and caring brother to your sister Zelda and your brother Thor." Recalling the furry family member's final moments, the post's caption read:

"Even at the very end when your body and mind were failing and beyond exhausted, you still tirelessly struggled to hold on for us, refusing to give in.  It was our turn to be selfless and strong for you. Tearing our own hearts out so we could help you to avoid suffering was the only loving option we had."

The reality stars described saying goodbye to Niko as "the hardest thing we have ever done" before expressing how much of a vacuum his loss has caused in their lives."

"We miss you so much already, but you’re at peace now. We know you are still with us, just in a different form. We struggle to find the words to describe our feelings for you, because nothing can express the love and joy that fill our hearts, where you will always remain," they wrote.

The heartfelt tribute was concluded with the real estate mogul and the Oppenheim Group agent writing, "You have changed our lives forever. Until we make it to where you are, we are sending you all of our love, you are forever and always our baby boy. Our bubby, Our Niko."

Other cast members of the real estate reality show took to the comments section to share their condolences. Nicole Young penned, "The sweetest boy ? I’ll love you forever my little nephew. My heart hurts for you and Mary…losing a dog is a heartache like no other."

Jason's twin brother, Brett Oppenheim, wrote, "Was the best baby boy, and he had an amazing life. Love all three of you forever," while a sympathetic fan penned, "I'm so so sorry for your loss. It's one of the saddest losses I think. Your furbabies are the most unconditional love ❤️ at least he is running forever now in a glorious place."

Another comment read, "So, so sorry. This is your family member, not just a pet. Devastated for you ?."

Jason Oppenheim and Mary Fitzgerald rescued Niko and Zelda, two long-haired chihuahuas, when they were dating years back. Before his death, Niko held the position of Director of Public (Pup-Lick) Relations at The Oppenheim Group.