in the book to kill a mockingbird, who are the mockimgbird

There would be two. One would be Boo Radely and the other would be Tom Robinson. Both tried to “do good”in the world. Both were beautiful inside and yet they were both punished. They are both innocents. The whole idea of "mockingbirds" stems from Atticus pointing out that "it is a sin to kill a Mockingbird" simply because they sing and provide pleasure to people. Both Boo and Tom, although they do not sing, have the innocence of the Mockingbird at heart yet are fragile in a very harsh society.