Answer:
Romeo's love for Rosaline.
Lord Capulet's plan to have Juliet marry Paris.
The feud between the Capulets and Montagues.
Step-by-step explanation:
Romeo is in love with Rosaline in the beginning. He sees Juliet for the first time when trying to see Rosaline.
Lord Capulet plans to marry Juliet to Parris in order to make her happier or at least to give her a purpose, which causes quite a few problems for the main characters during the play.
The Capulet-Montague feud is something that basically goes on throughout the whole story.