The family acts as a unit, so it thinks that the singular belongs. The subject-verb agreement refers to the fact that the subject and the verb correspond in a single sentence, either in the singular or in the plural. As with the bank, we could use a plural form with the company, the company, the association, the company. We treat even more often as plural the team, the government, the choir, the orchestra, the group, the class. It is also difficult to use the Neutrum Pronomen it or its in relation to a couple – so, if the pair is the precursor of a pronoun, we choose the pronoun she or she and use a pluralist for consistency.