Two of Three was a hologram, an altered version of Three of Eight, who was in turn based on Seven of Nine. Three of Eight was a character in a holonovel written by The Doctor, later altered by Tom Paris, entitled Photons Be Free. Two of Three, along with her sisters One of Three and Three of Three, were triplets who served aboard the USS Voyeur.
In the version of Photons be Free altered by Tom Paris, the EMH character, a sleazy character with a terrible bedside manner, giving her a Klingon aphrodisiac and massaging her neck. The Doctor was appalled by his fictional counterpart's behavior, describing Paris' modifications as amounting to "an insulting farce." (VOY: "Author, Author")