Dragons don't do friends. But why is that? The concept of friendship as it is understood in Equestria doesn't really exist in dragon society. Dragons have acquaintances and family, not friends, even if they sometimes use the word 'friend'.
For dragons, an acquaintance is a dragon they will spend time with but only when it's convenient. Dragons don't trust acquaintances and they wouldn't get out of bed for them if they needed anything. Dragons who only see each other when they gorge surf are a typical example of acquaintances. They meet, sometimes regularly. But this is not because they really want to see each other, it's because they are all doing the same thing and it's fun.
What if a dragon starts to care about an acquaintance, though? In dragon culture, this is when the acquaintance becomes family.
When dragons form very close friendships they may even adopt each other as siblings. This is what Smolder and Garble's grandfather, Ray, did when he and Torch became best friends. By extension, Caldera and her sister Tephra became Torch's nieces — and since Grandma Griddle adopted Torch as a son, Ray also got a mother and two sisters out of this.
Dragon Ray and Torch continue to climb mountains together as they did when they were acquaintances.
In the human world, Ray has passed away. He owned and operated Ridgelands Rock Climbing Gym until his death. Unbeknownst to his grieving family and friends, he was reincarnated as a leopard gecko.
Human Ray and Torch were close friends in the Equestria Girls-verse as well, so their families often go on trips together.