A more thorough explanation:

A void marriage is a marriage that is considered invalid from the beginning and cannot be made valid. This means that legally, the marriage never existed. There are several reasons why a court may declare a marriage void, such as if the marriage is incestuous or polygamous.

If two siblings were to get married, their marriage would be considered void because it is incestuous. Similarly, if someone is already married and tries to marry another person without getting a divorce first, their second marriage would be considered void because it is polygamous.

It is important to note that a void marriage is different from a voidable marriage. A voidable marriage is a marriage that is considered valid until one of the parties involved takes legal action to have it declared invalid.