Congener (from Latin congener "of the same race or kind," from com- "together" + gener-, stem of genus "kind") has several different meanings depending on the field in which it is used. Colloquially, it is used to mean a person or thing like another, in character or action.
In biology, congeners are organisms within the same genus. A related term -- referring to members of the same species -- is conspecific.
In chemistry, congeners are related chemicals, e.g., elements in the same group of the periodic table, or derivatives thereof.
In the alcoholic beverages industry, congeners, also known as fusel oils, are substances produced during fermentation