Why is Misha such a good friend to the orphans?

The first and most obvious answer to this question is that Misha is an orphan himself. Also, it is thanks to other people on the outskirts of society, such as Misha's friend Uri, that Misha gains an identity and a sense of community.
Misha's nature appears to be a gentle one, and he is kind to all those who are kind to him, resorting to criminal activities only as a means of survival for himself and those that he cares about.
I would argue that Misha was a good friend to anybody who showed him kindness and acceptance. For example, consider the way Misha treats Janina and her family, ensuring that they have food and following them into the ghetto in spite of the fact that he was not Jewish and therefore was not required to.

I believe that one of the best supporting pieces of evidence as to why Misha is such a good friend to orphans is that Misha was himself an orphan. When the novel begins, Misha does not even have a real name. He believes that his name is "Stopthief" because that is what he hears people calling out to him right after he steals something from them. Uri befriends Misha, and for the first time in his life, Misha has something that resembles a loving and supporting family. Uri will eventually give Misha the name "Misha," and Uri also provides him with a hypothetical background. Misha is thankful for people like Uri and Janina, and he is kind to orphans as a result. He has a heart for orphans because he knows what it is to be one, and being kind to them is his way of paying it forward.