By baby brother...Autobiography?

You don't need to exclude him (and you don't need a psychologist). Simply state that when you were six years old your brother died, that it is the most difficult thing you have ever had to face, that you are still grieving - you state your feelings well in your question - and that it is just to hard to talk about yet. He was and still is a part of your life and a part of your family, but you don't have to go into excruciating detail in this biography.