An ancestor is a person from whom one is descended. Usually it refers to a remote person, rather than the immediate parents or grandparents. A very similar word is forebear. A female ancestor may be called an ancestress. The line of people from whom a person descends is referred to as their ancestry.
A second meaning relates to evolution. There, it is used of an animal or plant from which others have evolved. In a similar way, it can be used for an early prototype or forerunner of a later device.
In law an ancestor can mean the person from whom an estate is lawfully obtained. No blood relationship is necessarily implied. More commonly, however, it is the person from whom an estate is obtained based on law and blood.
Two people have a genetic relationship if one is the ancestor of the other, or if they share a common ancestor. Each of someone's ancestors will have contributed to their DNA. In evolution, species that have evolved from the same ancestor are said to be of common descent.

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