Shakespeare meant for his plays to be performed on a stage and not to be read, he was a very skilled play write and he made his audiences believe things that in reality could not happen in such a short space of time. Romeo and Juliet's love for one another shows their disobedience towards their parents. The houses that the pair of 'star cross'd lovers' belong to are involved in an 'ancient' feud. We are made aware of the feud before we even meet the lovers; it is the very first thing that the Chorus, who is...
sure that the blame is shared; he makes that very clear:

'Where be these enemies? ?óÔé¼ÔÇ£ Capulet! Montague!

See what a scourge is laid upon your hate,

That heaven finds means to kill your joys with love;

And I, for winking at your discords too,

Have lost a brace of kinsmen. All are punished.'

The prince is also blaming himself; he knows that all had a part to play is Romeo and Juliet's deaths, and this is why it is such a tragic ending which is written in a very expert way.