The Catholic Encyclopedia (of 1907) may have useful information for you.
The institution of nuns and sisters, who devote themselves in various religious orders to the practice of a life of perfection, dates from the first ages of the Church, and women may claim with a certain pride that they were the first to embrace the religious state for its own sake, without regard to missionary work and ecclesiastical functions proper to men. St. Paul speaks of widows, who were called to certain kinds of church work (1 Timothy 5:9), and of virgins (1 Cor., vii), whom he praises for their continence and their devotion to the things of the Lord. The virgins were remarkable for their perfect and perpetual chastity which the Catholic Apologists have extolled as a contrast to pagan corruption (St. Justin, “Apol.”, I, c. 15; Migne, “P.G.”, VI, 350; St. Ambrose, “De Virginibus”, Bk. I, C. 4; Migne, “P.L.”, XVI, 193). Many also practiced poverty. From the earliest times they were called the spouses of Christ, according to St. Athanasius, the custom of the Church (“Apol. ad Constant.”, sec. 33; Migne, “P.G.”, XXV, 639).
There is quite a bit more, but the short story is that these individuals eventually started living together.