One thing that is significant about most of the main characters in Romeo and Juliet is that unlike the key characters in other plays by William Shakespeare, they are rather fully developed and interesting round characters, who display a wide range of emotions and various personality traits.
That Romeo and Juliet are human in their personalities is obvious. However, the portrayal of the priest, Friar Laurence is certainly a deviation from the typical religious leader of a community. For, Friar Laurence has not lost touch with the secular world and the deviousness that exists in it. For, in his good intentions of uniting Romeo and Juliet in holy matrimony so that they do not sin together, he also is involved in a circuitous plan to unite the families with Juliet's apparent death.
Similarly, the foolish, prattling Nurse displays what seems an incongruous personality trait. When she pragmatically advises Juliet to go ahead and marry Count Paris, the Nurse figures that Romeo, now banished, will never return to Verona and can no longer be of any use to Juliet.
The sanguine Benvolio, whose very name characterizes him, breaks through what appears to be his stereotype by displaying even more cholera than Mercutio at the beginning of Act III as he tells Mercutio that if he meets the Capulets he will not escape a brawl: "For now these hot days is the mad blood stirring"(3.1.4). And, Mercutio pointedly remarks about this uncharacteristic heat in the peace-loving Benvolio,
Thou art like one of these fellows that, when he enters the confines of a tavern, claps me his sword upon the table and says ‘God send me no need of thee!’ and by the operation of the second cup draws him on the drawer, when indeed there is no need.(3.1.8-10)Another main character who displays much humanity is Prince Escalus, who after the opening brawl between the Capulets and Montagues and having decreed that anyone who breaks the peace will do so under penalty of death, rescinds this decree after Romeo slays Tybalt and banishes him instead.
Of course, Lord and Lady Capulet move from being the doting parents to becoming the demanding insensitive aristocrats who desire the propitious marriage arrangement for their daughter.
Indeed, it is in part because of these well-developed characters that the readers/audience of Romeo and Juliet suspend any disbelief in the swift sequence of events of the tragic plot of Shakespeare's poetic play.