In Act I, Scene I of Romeo and Juliet, Montague only engages with the characters briefly, but in his few lines, there is evidence that he is not a static character.
Though he is often portrayed as a stubborn and single-minded old man, Montague does not simply have revenge on his mind. This is evident when he enters upon the scene and although he is ready to engage in the fray, heeds the Prince's command to "depart away" and to meet with him later to discuss the cause of the civil unrest.
In addition to his ability to forgo fighting (albeit to save his life, because the Prince also threatens both Montague and Capulet that "If ever you disturb our streets again, Your lives shall pay the forfeit of the peace"), he too asks the question, "Who set this ancient quarrel new abroach? / Speak, nephew, were you by when it began?" This implies Montague is not in support of the fights that have disturbed the peace and occurred in the streets. He may support a feud between the two houses, but he does not support acting upon the feud. His inclination to seek Benvolio's account of how the fight began reveals that Montague does seek the truth. As the play develops, we as readers also trust Benvolio's character and his judgment.
Lastly, in his final words with Benvolio, Montague seeks his advice and help a second time. This time it is in regard to his son Romeo. Montague admits he often sees Romeo
With tears augmenting the fresh morning dew.
Adding to clouds more clouds with his deep sighs...
Shakespeare's use of figurative language depicts a young man who cries often and heavily due to his melancholy state. Rather than being upset with his son for being emotional, Montague wants to know the source of his son's discontent. He admits that he cannot get Romeo to admit why he is upset to Montague, and that Montague has employed "many other friends" to try and counsel Romeo but to no avail. Finally, he informs Benvolio, "Could we but learn from whence his sorrows grow, We would as willingly give cure as know."
This illustrates that Montague is not simply a hardened man who seeks to perpetuate an endless feud. He is a father whose main concern is the well-being of his son. Secondly, he is a citizen who adheres to the laws dictated by the kingdom and wishes to maintain a level of peace for the citizenry.