'Next friend' definitions:

Definition of 'next friend'

noun

(law) a person who acts on behalf of an infant or disabled person

From: GCIDE

Next \Next\ (n[e^]kst), a., superl. of Nigh. [AS. n[=e]hst, ni['e]hst, n[=y]hst, superl. of ne['a]h nigh. See Nigh.]
1. Nearest in place; having no similar object intervening. --Chaucer. [1913 Webster]
Her princely guest Was next her side; in order sat the rest. --Dryden. [1913 Webster]
Fear followed me so hard, that I fled the next way. --Bunyan. [1913 Webster]
2. Nearest in time; as, the next day or hour. [1913 Webster]
3. Adjoining in a series; immediately preceding or following in order. [1913 Webster]
None could tell whose turn should be the next. --Gay. [1913 Webster]
4. Nearest in degree, quality, rank, right, or relation; as, the next heir was an infant. [1913 Webster]
The man is near of kin unto us, one of our next kinsmen. --Ruth ii. 20. [1913 Webster]
Note: Next is usually followed by to before an object, but to is sometimes omitted. In such cases next in considered by many grammarians as a preposition. [1913 Webster]
Next friend (Law), one who represents an infant, a married woman, or any person who can not appear sui juris, in a suit at law. [1913 Webster]