In a recent article on Ruth 1:16-17 in CBQ , Mark Smith comments on the relation between covenantal and familial terminology in Ruth and elsewhere. Even when covenants have political dimensions, as in international treaties, they are fundamentally mechanisms for extending kin ties beyond immediate blood relations. Smith writes:

“A great deal of this treaty or covenant vocabulary clearly was family vocabulary, by which the parties to the treaty expressed their relations in familial terms—‘father’ and ‘son’ in vassal treaties, ‘brother’ in parity treaties. In these instances, treaties established relations between two monarchs who were
unrelated in terms of family lines. The larger world of ruling monarchs could be understood as a large family or a series of families, in which each king knew his place, whether as overlord, equal, or vassal. Family was, to use Mary Douglas’s expression, a “natural symbol” for expressing these sets of relations. This conceptual usage was not restricted to narrow family terms but extended to other expressions at home in the family, such as the language of love and familiarity (or literally, ‘knowledge’).”

He adds, “it often escapes scholarly attention that covenantal relations could take place at all levels of society and not only in the settings most conspicuous from newly discovered texts, namely, the international relations among royal courts. Covenant is a mechanism useful for family life, to extend relations beyond the family, or even to intensify relations within family life (e.g., Gen 31:44-50).”

And he quotes Frank Moore Cross’s comment: “Often it has been asserted that the language of ‘brotherhood’ and ‘fatherhood,’ ‘love,’ and ‘loyalty’ is ‘covenant terminology.’ This is to turn things upside down. The language of covenant, kinship-in-law, is taken from the language of kinship, kinship-in-flesh.”