Benvolio represents brotherly love. He has as much reason as Romeo to be sad, but he never shares his sorrow. He wants to keep the peace, and he wants Romeo to "be ruled by [him]"--that is, follow his advice and look at other girls. He acts as a true guy friend would act.
Romeo represents cupiditas, or lustful love. He is the "romantic" lover, always looking for someone to return his affections. He is like the fireworks the Friar speaks of--quick and explosive to love.
Romeo's servant is faithful love or loyalty. Balthazar rides for miles to give Romeo the news of Juliet's death, and he stays near the tomb even after Romeo tells him to leave because he is concerned about Romeo's well-being.
Montague parents represent familial love. They both care deeply about Romeo. They are observant and they know he is depressed, but they can't get him to talk to them. Kind of like the love between parents and teenagers now.
The Prince represents caritas, or the love of mankind. He rules justly, with a kind heart, but with an eye also to keeping the peace. He is willing to sacrifice one of his subjects for the good of the whole community.