[bazoom42]

> The play begins with Romeo utterly in love with Rosaline - what's that for if not to show us not to take his feelings for Juliet too seriously

Rosaline is a nun and therefore pure and unattainable. Shakespeare is lampooning the genre of “courtly love” where the poet is longing but the love never consummated. Romeos “heavy lightness”-poem is a satire of this genre.

This is contrasted with the love for Juliet which is real and physical. Notice how Romeos poetry becomes a lot better when he meets Juliet.

The complaints that Romeo and Juliets love is “not real” (because of physical desire and sex) is really an echo of the ideals of courtly love, which Shakespeare ridicules.

> And Juliet's 13 - which was very young for marriage even at that time. Certainly not what would have been considered 'adult' then

This is specifically adressed in the play. Juliet is consideret of appropriate age for marriage, and is already being set up with Paris before she meets Romeo.

Of course she is just a child by modern standards, but that is irrelevant for understanding a 400-year old play.