What threats already exist to Romeo and Juliet's love in Act 1?
There are a number of threats to Romeo and Juliet's love in Act I. First of all, there is the feud between the Montagues and Capulets. This bitter divide between the two families, which frequently erupts into violence, threatens their love because it casts Romeo and Juliet as sworn enemies.
Secondly, Rosaline also threatens Romeo and Juliet's love. In Act I, Scene I, for example, Romeo is heartbroken because Rosaline does not reciprocate his feelings. However, by swearing that she will never love Romeo, Rosaline also paves the way for Romeo and Juliet's union, thereby switching this threat into a favorable condition.
Finally, Paris also provides a threat to Romeo and Juliet's love. In Act I, Scene II, for instance, the reader learns that Paris has already asked for Juliet's hand in marriage. If she were to go ahead with a marriage to Paris, she would never have the opportunity to be with Romeo and fall in love with him.