Something to call a step dad?

Put yourself in her shoes, she is probably coping as well as she can with the change. I know it's not the best situation for you and your brother, but calling him dad is helping her cope with the situation. She is only 4 and is doing what she can to make things fell right for her, so try to understand and don't worry about it because she be will around for sometime so try to cope with it for know and everybody will hopefully benefit.