While it is clear that Romeo is very close with his cousin Benvolio who is also his friend, as well as his friend Mercutio, it's also very evident that Romeo and his friends have very different views on things. In fact, Benvolio and Mercutio act as two different dramatic foils to Romeo.
Benvolio serves as Romeo's dramatic foil by being the peace-loving, rational, voice of reason in comparison to Romeo who is impetuous and emotionally driven. We see the closeness of their friendship when Benvolio promises Lord Montague to find out what is troubling Romeo in the very first scene and to give him counsel. However, their dramatic foil relationship also becomes evident when Benvolio begs Romeo, "Be rul'd by me: forget to think of [Rosaline]," and Romeo's only response is "O, teach me how I should forget to think!" (I.i.227-28). Romeo's refusal to listen to Benvolio also shows us his refusal to think rationally, which helps us see their dramatic foil relationship despite their close friendship.
Mercutio serves as Romeo's dramatic foil by taking love lightly and treating it as a joke in contrast to Romeo's tendency to treat love with complete seriousness. Like Benvolio, Mercutio's close friendship with Romeo is also seen in his desires to give Romeo advice and bring him out of his gloomy state of mind. Mercutio tries to coax Romeo out of his gloominess by trying to persuade him to crash the Capulets' ball along with Benvolio. His persuasion techniques not only show us his friendship with Romeo, they also show us his comic and even lewd side, demonstrating just how lightly he views love. One example can be seen in the lines, "If love be rough with you, be rough with love. / Prick love for pricking, and you beat love down," which can be interpreted as a sexual innuendo (I.iv.28-29).
Romeo has a great bond with mercutio almost as they are brothers and constantly talks with him throughout the book. At one point the both of them go to a party where romeo meets juliet. But near the end of the book mercutio is killed by tybalt which strikes an anger in Romeo so great that he kills tybalt and avenges mercutio
As for benvolio... i dont remember :p