Final answer:
Sue's brothers and fathers belong to a primary group, which is defined by close emotional bonds and significant personal interaction, with the family being a classic example of such a group.
Step-by-step explanation:
Sue's brothers and fathers are members of a primary group because they are emotionally close and spend a great deal of time together. Primary groups are characterized by intimate, face-to-face association and cooperation; they are typically small, include personal and enduring relationships, and serve emotional needs. The family is the quintessential example of a primary group, despite the fact that today, physical proximity may not always define these relationships due to technological advancements allowing for maintained emotional connections across distances.