River, growing up, was much like their name. They went with the flow of whatever happened around them. For some reason, they had always thought they might be the cause for their mother leaving them shortly after they were born. The three kits were nursed just barely long enough, and then she was gone, forever. She had always come in smelling of hostility and fear, which put River on edge, and molded them into the cat who always tip toed around others even as a kit. This continued especially after their father passed, too sad to carry on without their mother. Feather was always so headstrong and fast, catching as much prey as she could for all three of them. Boulder was big and stocky and always prepared to jump to protect them from anything. River... Sat back and watched. River was the quiet, babbling brook behind the trio, gently herding their siblings here and there to take the rest when needed. They had lost their parents already, there was no reason to lose each other.
So when they did... River was devastated. Boulder shoved River out of the way of a rockslide, and got crushed under the rocks. River dug for days before they could finally reveal their siblings corpse and bury it properly. By then, Feather was already week. She had been running ragged feeding all three of them, and even though they had lost Boulder, it wasn't enough to allow her to regain her strength from their catches.
River was suddenly alone. All alone in the once crowded and noise filled den. Barely an adult, they found the forest to be far too big now. Where were all the other cats? Stories of clans had been told to the trio of kits growing up, but the way their parents smelled when talking about them... Especially their mother, the fear that gripped her... River would not go to a clan. At least, not the clan their mother came from.
But.... They missed their family. They missed the comradery. The sense of belonging and being happy. Everything was bleak and dark now. River just wants to feel the warmth again.