Final answer:
The third major influence on our identity is communication with peers, which is essential in shaping our social skills and sense of belonging, although the family is often the first and most important influence on political socialization.
Step-by-step explanation:
The third major influence on our identity, according to the textbook, is communication with peers. Peer interaction is a critical component of socialization, helping to shape identity, attitudes, behaviors, and social skills. This is because peers often provide a space for individuals to express themselves and experience a sense of belonging. While family members and self-communication play significant roles, the influence of peers is underscored by the social learning and comparisons that occur within peer groups during adolescence.
In contrast, when considering the most important influence on political socialization, the family is typically considered the primary agent. As for the earliest agent of socialization, the family is also generally recognized as the first social structure that begins influencing an individual from birth. Though factors like gender and class are significant for overall socialization, the direct interactions with family and peers are particularly pivotal in shaping political opinions and values.