There are several synonyms for the term "second selves," which refer to individuals who act and behave similarly to oneself. One such synonym is "alter ego," which denotes another facet of one's personality or character that is distinct from the primary one. Another term that can be used interchangeably with "second selves" is "doppelganger," which typically describes an exact physical copy of oneself that appears in a parallel universe or alternate reality. Additionally, terms like "twin soul" or "kindred spirit" can be used to refer to individuals who share a similar outlook or worldview with another person. Finally, the term "shadow self" denotes the darker, more unconscious aspects of one's personality that are often repressed or hidden from sight.