All three women came from backgrounds where there were no men available as spouses to them. They were manipulated by Mudd into consuming the Venus drug, which seemed to make them more attractive in appearance.
In 2266, the women were being ferried to Ophiucus III by Mudd when they were intercepted by the USS Enterprise. The trio of females had a mysterious magnetic effect on the male members of the starship's crew. Ultimately, however, they were married to lithium miners on Rigel XII, where Mudd and the Enterprise left the women. (TOS: "Mudd's Women")