Romeo being banished, yes or no?

Personally, I don't agree with Romeo's punishment. Being banished for killing Tybalt was wrong, yes. However, Juliet's family has killed some of his before and vise versa. Why banish him if Juliet's family has done the same thing to his? It isn't fair. Although Romeo killed Tybalt, he doesn't deserve to be banished. If anything, he deserves a punishment of some sort, but nothing like what they're trying to do to him.