How does the hateful relationship between the families in "Romeo and Juliet" affect their children negatively?

Most
directly, the "hateful relationship" of the two families causes the death of . 
Thetells us this:

From forth the fatal loins of these two
foes
A pair of star-cross'd lovers take their life;
Whose misadventur'd
piteous overthrows
Doth, with their death, bury their parents strife.
The
fearful passage of their death-mark'd love,
And the continuance of their parents rage,

Which, but their children's end, naught could remove,
Is now the two hours
traffic of our stage;

It is the death of the children
that ends the "parents' strife."  Nothing else could make the rage go away.

How does it all come about?  Whenandmeet, there is an instant connection that is
shortly built to love in their minds.  They are both distraught to discover that the other one
belongs to the "enemy."  However, Romeo sneaks into the garden of the Capulets and
meets with Juliet at her balcony.  This fuels their attraction and love, and makes them eager to
overcome...