Irish History From The Annals
A common institution in medieval Ireland was fosterage.
Fosterage involved one family giving their children to another to be raised. Once the fosterage arrangement had been agreed the two kin groups would be linked politically and socially. Any injury suffered by the fostered child also impactedthe foster family and the foster family could count on the military support of the fostering family. In 1554 The Annals of the Four Masters recorded the great eraic received by the Earl of Kildare for the death of his foster brother.
A great fine in cows, namely, three hundred and forty cows, was apportioned upon and obtained from Delvin-Eathra by the Earl of Kildare, as an eric for his foster-brother, Robert Nugent, who had been slain by Art, the son of Cormac Mac Coghlan.
Fosterage was away of extending political power. For example in the obituary of Brian O’Rourke in 1562 the Annals of the Four Masters noted:
O'Rourke (Brian Ballagh, son of Owen), the senior of Sil-Feargna, and of the race of Aedh Finn, a man whose supporters, fosterers, adherents, and tributaries, extended from Caladh, in the territory of Hy-Many, to the fertile, salmon-full Drowes, the boundary of the far-famed province of Ulster; and from Granard in Teffia to the strand of Eothuile, the Artificer, in Tireragh of the Moy,—
Fosterage could also be forced upon a sept by a more powerful family. For example the Annals of the Four Masters record that in 1554 the O’Brien forced Meyler Burke to give him fosterage.
A hosting was made the week after this by O'Brien into Clanrickard; and he committed a great depredation upon some people of that country. From thence he proceeded to Dun-Lathraigh in the county of Galway, to which the descendants of Richard Oge and the descendants of Meyler Burke repaired, and received fosterage and wages from him.
The Irish clergy also took foster children and the Annals of the Four Masters record in 971 that:
Dunchadh, the foster-son of Diarmaid, distinguished bishop and chief poet of Osraighe, died.