Romeo is their only son. They love him dearly and, as the play opens, are very concerned about him. He has been acting depressed, holing himself up in his room where he makes himself an "artificial day," and not talking to anyone. They don't know what the trouble is, and they share their concerns with his friend and cousin Benvolio. His mother does mention how happy she is he was "not at this fray" - the fight in the street that has just taken place.
Benvolio, too, has noticed Romeo's moodiness, and he promises to speak to Romeo and try to find out the cause. During this conversation, Benvolio learns that Romeo is sad because he loves (or thinks he loves) Rosaline, and she doesn't love him in return. It is here Benvolio promises to help Romeo forget Rosaline, and they decide to crash the Capulet party that evening.
Romeo's parents don't show up again until after Romeo has killed Tybalt, and his parents are begging the prince for mercy. They do everything they can to argue on his behalf. Romeo's father, Lord Montague, points out that Mercutio was Romeo's friend and that his killing of Tybalt was justified, for "his fault concludes but what the law should end: the life of Tybalt!" The Prince agrees not to kill Romeo, but instead banishes him from Verona.
Romeo never gets the chance to tell his parents goodbye. He does write a letter, which he gives Balthasar to give to his parents, before he kills himself. In the final scene, we see his father in despair, having lost both his son and his wife (who died of grief at Romeo's banishment, showing just how much she loved him). However, there is a glimmer of hope at the end as the two fathers pledge to build statues of Romeo and Juliet, bringing an end to the feud which has cost them both dearly.