Contrary to popular belief, the original form that paired with the singular “thee” was not “you,” but rather “ye.” “You” was originally used only in objective forms, such as accusative or dative. The shift from “ye” to “you” as a nominative form happened in the 15th century, while “ye” began to be used as an objective form. Nowadays, “ye” is only used in dialects, archaic language, or poetry. It is interesting to note that “you” was originally used as the plural form of “thou” in the accusative and dative cases. There is a lot more information available in the Oxford English Dictionary entries for “ye,” “thou,” and “you.”
https://english.stackexchange.com/questions/9780/did-english-ever-have-a-formal-version-of-you