Your question required quite a bit of editing in order to focus your query. I have related this version of your question to the Comedies, of which, Romeo and Juliet is not one. Please re-frame your question as it relates to Romeo and Juliet and resubmit for answer.
Love in Shakespeare's Comedies follows a pretty strict structural set of rules. There are lovers introduced in the opening scenes of the play who sometimes fall in love at first sight. Sometimes, one character must attempt to "win" the love of another character. And sometimes, they are characters engaged in a battle of the sexes, but who are in love beneath their barbed words.
In Twelfth Night we have a variety of these types of lovers: Olivia and Viola both fall in love at first sight --Olivia with Viola (who is disguised as Cesario), and Viola with Duke Orsino. Sebastian also enters this play and falls in love with Olivia at first sight. There are also lovers in this play attempting to win their beloved's affection. Both Andrew Aguecheek and the Duke are after Olivia's hand in marriage. And there is also a bit of the battle of the sexes going on between Sir Toby and Maria.
In Much Ado About Nothing, Hero and Claudio fall in love with each other at first sight, and Beatrice and Benedick are engaged in a battle of the sexes that masks their true feelings for each other. Both of these pairs of lovers have their situations complicated by deceptive tricks that have a huge impact upon their feelings.
The Tempest, while not a traditional Comedy, does contain a very traditionally comic pair of lovers -- Ferdinand and Miranda. They fall in love at first sight, and are the vehicle whereby their estranged fathers are reconciled to each other. The interesting addition in this play, is the onstage "magic," created by Prospero, that visibly draws the two lovers together.
Each of the above mentioned Comedies (and the pair of lovers in The Tempest) is required to end in reconciliation and at least one marriage. In Twelfth Night, all the mistaken identities and mis-applied feelings of love are sorted out, and the play ends with three marriages: Viola and the Duke, Olivia and Sebastian, and Sir Toby and Maria. In Much Ado, the complications are sorted out as well, and the play ends in the weddings of Hero and Claudio and Beatrice and Benedick. And in The Tempest, the play also ends in plans for the wedding of Miranda and Ferdinand.
For more on love in Shakespeare's Comedies, please follow the links below.