It is hard to say exactly why Robert F. Kennedy was assassinated given that Sirhan Sirhan clearly had serious psychological problems. However, there is a way of arguing that Kennedy’s assassination was indirectly connected to the fact that his brother had been a very famous president.
In one sense, RFK’s assassination was not connected to his brother. Sirhan was supposedly motivated by RFK’s support of Israel. Sirhan was of Palestinian descent and had anti-Israel opinions. He claimed to have killed RFK because of those opinions. RFK’s stance on Israel was not caused by his brother. Therefore, we can say that RFK was not killed because of JFK.
On the other hand, if we think of Sirhan’s psychological problems as the real cause of RFK’s death, we can say that JFK helped bring that death about. In this view, Sirhan killed Kennedy not because of Kennedy’s political views but because Sirhan wanted to call attention to himself in some way. If this is what Sirhan wanted, Kennedy was a better target than most other politicians because he was JFK’s brother and a member of the most famous family in American politics at that time.
Thus, we can say that JFK might have had an indirect role in causing his brother to be assassinated.