doppelgänger [dop-uh l-gang-er]
1. A ghostly double of a living person, especially one that haunts its fleshly counterpart.
2. Either of two people who physically resemble each other very much.
When I was a kid I worried that when I woke up, I'd find my family having breakfast with my doppelgänger. We would fight to the death, and then my family would peacefully finish breakfast. (Fran Krause, Deep Dark Fears)
Many people say, "Who's my doppelganger?' when maybe
they should ask, "Whose doppelganger am I?"
Repeat meetings, specifically three, always meant that the end was near. If someone else saw your doppelgänger, it could mean that you may be very ill." (Linda Derry, quoted in Tom Little's Tracing the Development of the Doppelgänger)
German, a double : doppel, double (from French double) + Gänger, goer (from Gang, a going, from Middle High German ganc, from Old High German). (The Free Dictionary)
According to age-old German folklore, all living creatures have a spirit double who is invisible but identical to the living individual. These second selves are perceived as being distinct from ghosts (which appear only after death), and sometimes they are described as the spiritual opposite or negative of their human counterparts. In 1796, German writer Johann Paul Richter, who wrote under the pseudonym Jean Paul, coined the word Doppelgänger (from doppel-, meaning "double," and -gänger, meaning "goer") to refer to such specters. (Miriam-Webster)