Male bonds are funny things in Julius Caesar. Men in the play must to choose between loyalty to their friends and loyalty to the Roman Republic, which leads to some of the most famous examples of manipulation and violent betrayal in Western literature. This is especially true for Brutus, who chooses to join the conspirators' assassination plot when it seems clear to him that his BFF, Julius Caesar, is headed for absolute power.
Although male friendship is the most important human relationship in the play, it's less important than loyalty to the Roman Republic.
It's nearly impossible to tell the difference between friends and enemies in Julius Caesar.