I have recently had a DNA test and have a shared match of 1957 over 50 segments with one of the matches. They are not interested at the moment in communicating. I was brought up as an only child, so it cannot be a niece or nephew. It cannot be a grandparent as they are not alive and haven't been for along time.
Is it likely that this person is a half-sibling?
If so how do I find out whether it was my mother's child or father's child?