Their families are another thing. Their love was probably based on lust, but, when they found out that their families were sworn enemies, that probably fueled them forward. There's nothing like forbidden fruit, right? Juliet was also possibly looking for a way out of her arranged marriage, and marrying Romeo was a perfect way out of her family. For Romeo, he was just trying to get over that other girl. He was being pretty emotional, and probably wasn't really being himself. He was just looking for some kind of replacement. The thig about Romeo and Juliet is that the duo is old enough to think they know everything but young enough to not know anything. They are so cauht up in the moment that they can't see what's right and what's wrong, and so, they end up killing themselves for the other.
What they have is a combination of infactuation, lust, and mutual attraction. Both were looking for a way out of their lives, and found an ideal way in their partners. Caught up in the moments and still young and foolish, they ended up dying for each other. That's more or less their story.