Answer: I think that if Romeo would never have met Juliet then there would be no love story at all! I also think that Romeo would just spend his entire life alone. They also love each other so much that believing that Juliet is dead he buys poison and dies while Juliet wakes up and found out that he died then she stabbed herself and they both died. This may not sound like a happy story but they both died know that their love was everlasting. So to conclude, their bond was unbreakable and they loved each other more than anyone else.
Answer to your 2nd question: Romeo and Juliet are in love but it wasn't exactly how there love blossomed. See Romeo fell in love with a girl named Rosaline and he tried to get over her because he really loved Rosaline. He also attended the Capulets' party to see Rosaline hoping that he could win her back. Romeo and Juliet never actually fell in love in the beginning because they were both searching for escapism. Juliet was the one who fell in love more because when he met her she reciprocates his love, so then he understands what it's like to be in love. So to finalize, not every story has to start out with a happy theme but like all fairytales, we all have a reason to fall in love with someone!