Second families

If your mother or father remarries, you can acquire a new family and set of relatives. For example, if your father marries a second wife, she becomes your step-mother. Any children she already has become your step-sisters or step-brothers.

If your mother or father remarries and has children, they become your half-brothers or half-sisters.

You might also hear people talking about their biological brother / sister etc, to mean a brother who is related by blood, rather than by marriage.(From http://www.english-at-home.com/vocabulary/talking-about-your-family/)

2. Study your family history. Create your family tree. Make up presentation. Choose the best one.