What defined JFK Jr was not himself as a Kennedy but people defining him as a Kennedy. His father died when he was very young, so he did not get his personality or his interests. But for his entire life, people treated him like he was JFK's son, and expected to be and do certain things. The powers that be absolutely would have wanted and pressured him to run for mayor of NYC, or senator. And he'd have no experience or qualification or likely interest to be either; he'd just have the name Kennedy and who he was born to. There is a role that, regardless of what he wanted to do himself, people expected him to go into.