Definition of Fosterage
Care of a foster child, brother, sister, parent, etc.—one considered as holding the relationship indicated in consequence of nursing and rearing, though not related by blood. In re Norman’s Estate, 209 Minn. 19, 295 N.W. 63, 66.
That's the definition of Fosterage in Black's Law Dictionary 6th Edition. Courtesy of Cekhukum.com.