[CONCERNING A CHRISTIAN WOMAN ABOUT TO BE MARTYRED:] She gave birth to a little girl, which a certain sister brought up as her daughter. Passion of Perpetua and Felicitas (c. 205, W), 3.704.
Although keeping parrots and curlews, the [pagans] do not adopt the orphan child. Rather, they expose children who are born at home. Yet, they take up the young of birds. Clement of Alexandria (c. 195, E), 2.279.
When any Christian becomes an orphan, . . . it is good for one of the brethren who is without a child to take the young man and value him in the place of a son. Apostolic Constitutions (compiled c. 390, E), 7.433.