There is another kind of friendship in which the parties are unequal (e.g., friendship between father and son, older and younger person, husband and wife, ruler and subject). These relationships vary depending on the differences between the parties (e.g., the relationship between parents and children is not the same as that between ruler and subject). In such relationships each party has his own distinct excellence and function, and has his own reasons for feeling affection. Both parties do not, and ought not, expect to receive identical benefits from the relationships (e.g., the duty of children to parents is not the same as the obligations of parents to their offspring).
In all friendships where the parties are unequal, the feeling of affection between them must be equalized according to a ratio or proportion (i.e., the more virtuous or useful of the two, in general whichever party is superior, should receive more affection than he gives). Equality is the essence of friendship, but it can only exist when the superiority of one party is balanced by an equivalent amount of affection from the other party.
Equality in justice is that which is proportionate in a qualitative sense, but in friendship it must be determined on a quantitative basis. The reason for this is illustrated by the fact that friends tend to drift apart when there are great differences between them in virtue, vice, wealth, status, or anything else. Thus, friends do not really wish the greatest of goods for each other, since the fulfillment of the wish would cause them to cease being friends. True friends are content to wish for each other the greatest goods appropriate to a human being in their particular circumstances, and perhaps not even all of these.