A doppelganger is a person that resembles, and looks like someone else, however, is not related to the first person.
Example of use: Don — “I saw Mark at the movies last night, but he didn’t seem to notice me when I called him. Do you know if he’s angry at me, and why?” Amos —”That’s so weird, cause Mark is on a business trip in India since last Wednesday. I think you saw his doppelganger.”
The term 'Doppelgänger' is derived from German, and its literal meaning is "Ghostly Double". Doppelgängers were considered to be omens of bad luck, and it was believed that when he was seen by either a person's friends or even by himself, it was an omen of illness, danger and even death. The term was first used by Jean Paul in the novel 'Siebenkäs' in 1796. However, its first appearance in English was in 1851, in 'The Denham tracts', a collection of folklore by M.A. Denham.