The original source for the claim that she was Socrates' wife appears to have been a work by Aristotle called On Being Well-Born, although Plutarch expresses doubt that the work is genuine. She was apparently the daughter, or, more probably, the granddaughter of Aristides.
Although Diogenes Laërtius describes Myrto as Socrates' second wife living alongside Xanthippe, Myrto was presumably a common-law wife, and Plutarch describes Myrto as merely living "together with the sage Socrates, who had another woman but took up this one as she remained a widow due to her poverty and lacked the necessities of life." Athenaeus and Diogenes Laërtius report that Hieronymus of Rhodes attempted to confirm the story by pointing to a temporary decree the Athenians passed:
For they say that the Athenians were short of men and, wishing to increase the population, passed a decree permitting a citizen to marry one Athenian woman and have children by another; and that Socrates accordingly did so.—Diogenes Laërtius, ii. 26