A cat named Simon has melted hearts on social media with his heartbreaking reaction every time his golden retriever sister goes out without him.

In a video shared on TikTok earlier in August, under the username @simon_and_darby, the cat can be seen standing on his owner's armchair in the living room, watching as the golden retriever, Darby, walks out the door alone.

As soon as he sees she's out, he starts meowing frantically, walking to the door as if asking his owner to go and look after her. "What Simon does when Darby goes outside," reads layover text on the clip.

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"Proof that pets get SO attached to their siblings...and worry when they aren't there," says a caption shared along with the heart-warming clip.

Despite popular belief painting them as nemeses, cats and dogs can actually be best of friends. The secret to this potentially special relationship is in the introduction.

Newsweek previously explained that taking things slowly will help toward avoiding bad first impressions and can set the basis for a lifelong friendship.

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They will each need their own space in the house where they can stay away from each other. It is also important to supervise your cat and dog when they interact until they're comfortable with each other. If you notice defensive behaviors, such as hissing or growling, you need to take a step back and give them more time.

The video quickly went viral on social media, getting viewers from across TikTok. It has so far received over 611,600 views and 51,100 likes on the platform.

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One user, U_ilani, commented: "When I take my dog outside my boy waits for us at the front door. It's so cute."

Patricia Maxine Cast said: "After seeing this, I therefore conclude... that the black cat CAN get clingy with the golden retriever too."

_queen1982 wrote: "The slide down the window was so dramatic," and the poster answered: "Academy award worthy lol!"

Another user, darksights, added: "Mine wants to be picked up when dog goes out and will whine till I do just so he can watch him outside safe in my arms."

Newsweek reached out to simon_and_darby for comment.

Do you have funny and adorable videos or pictures of your pet you want to share? Send them to life@newsweek.com with some details about your best friend and they could appear in our Pet of the Week lineup.