Who does Cinna want to join their group?

I can see that there are no choices.

Cinna wanted Brutus to join his group.

Explanation:

Cinna is one of Julius Caesar's conspirators.

While he was talking to Cassius, he tried to convince him to let Brutus (a noble Roman) join the group. Cassius then told Cinna that the matter would be taken care of smoothly if Cinna would plant fake notes to convince Brutus. The notes were to be placed on Brutus' chair and on the statue of his relative. It contained a message about how dangerous Caesar was as a leader of Rome and that Brutus was better than Caesar.

So, this explains the answer.