I Am Unable To Remember Anything From My Childhood And

I am unable to remember anything from my childhood and most of my life. I have a niece that has the same problem. I would not have known I had a bicycle as a kid if there wasn't a picture, graduating from high school, college, things done with my children, etc. According to my sister there is a medical name for my issue. I know nothing can be done for this issue, I'd just like to know what it is called. Thank You. Cynthia