A similar looking although considerably less attractive person who is included in activities in order to make their counterpart look better by comparison.
The doppelminger is often unaware of their status as doppelminger, or sometimes uses the relationship for their own advantages (for example, becoming cool by association)
Yeah but only because she'sgot her doppelminger with her.
Someone who jumps from one relationship immediately into another one.
Serial monogamists can not stand to be alone and often suffer from vast commitment and insecurity issues.
Because they jump into relationships immediately after the previous one has ended, serial monogamists typically don't take the time to reflect on their behavior or why their previous relationships failed; thus, they end up making the same relationship mistakes over and over again.
Person 1: Damn, Dustin already has a new girlfriend?! It's only been two weeks since he broke up with his fiance! I think he's a sociopath.