Fosterage, the practice of a family bringing up a child not their own, differs from adoption in that the child's parents, not the foster-parents, remain the acknowledged parents. In many modern western societies foster care can be organised by the state to care for children with troubled family backgrounds, usually on a temporary basis. In many pre-modern societies fosterage was a form of patronage, whereby influential families cemented political relationships by bringing up each other's children, similar to arranged marriages, also based on dynastic or alliance calculations. This practice was once common in Ireland, Wales, and Scotland.
Fosterage in Scotland
In medieval Highland society there was a system of fosterage among clan leaders, where boys and girls would leave their parent's house to be brought up in that of other chiefs, creating a fictive bond of kinship that helped cement alliances and mutual bonds of obligation. In his A Journey to the Western Isles of Scotland, writer Samuel Johnson described the fosterage custom as he saw it practised.
Fosterage in Medieval Iceland
Fosterage or "fostering" is frequently referred to in the medieval Sagas of Icelanders. Original family ties and rights of inheritance were not affected, nor was it required for the fostered child to be an orphan or for the biological father to be deceased. Moreover, the fostering of another man's child was regarded as a source of honor to the birth father; and conventionally the fostering party was of inferior social status to the biological father. An exception to this convention is found in Njáls saga, where Njál Thorgeirsson, a very prominent man, fosters Hoskuld, the son of Thrain Sigfusson, after the death of Thrain in battle. Portions of Ireland, Scotland and the Hebrides were ruled for long periods of time by Norse invaders during the Middle Ages; but it is unknown which culture was the original source of the custom of fosterage.
Literary fosterage
In Ancient Ireland, ollams taught children either for payment or for no compensation. Children were taught a particular trade and treated like family; their original family ties were often severed.
Fosterage in other cultures
There was similar custom in the Caucasus, called Atalik - :ru:Аталычество.
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Parkes, Peter. "Fosterage, Kinship, and Legend: When Milk was Thicker than Blood?" Comparative Studies in Society and History 46 : 587–615.
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McCutcheon, James, 2010. "Historical Analysis and Contemporary Assessment of Foster Care in Texas: Perceptions of Social Workers in a Private, Non-Profit Foster Care Agency". Applied Research Projects. Texas State University Paper 332. http://ecommons.txstate.edu/arp/332
Anglo-Saxon England
Crawford, Sally. Childhood in Anglo-Saxon England. Stroud: Sutton Publishing, 1999. Especially pp. 122–38.