He had no family members and was an orphan. He came to the island earlier than Xunuo and was a normal child back then. He then attended training and Wolf's methods were very scary. He had no ability to retaliate when he was young and felt like he was better off dead.
Even a grown man would not be able to go through that kind of high-intensity training, moreover the young him.
His whole body was always filled with injuries. Xunuo saved him on the first day that she came to the island. She was still a child that did not know anything and seemed lost, sad, and lonely. She did not even know him at that time but helped him distract the snakes and saved him. In the end, they found Xunuo at the back of the mountain and she was injured with snake poison.
The relationship between children was the purest. Ever since that day, Silver Cloud told himself that Xunuo used her life in exchange for his life. Therefore, she was the girl that he had to protect forever.