Final answer:
The partisanship of their parents is the strongest influence on young citizens' party identification, with children often adopting the political views of their parents, though peers and social media also contribute.
Step-by-step explanation:
The strongest influence on young citizens' party identification tends to be the partisanship of their parents. Children are more likely to adopt the political beliefs, attitudes, and behaviors of their parents, especially in households where parental engagement in politics is high, and party identification is strong. This is evident in early and recent findings showing that children often register with the same political party as their parents. However, with the growth of the internet and social media, peers and virtual networks also play a role in shaping political views, but the foundational influence appears to be from the family.