Shakespeare presents the fatalities of Romeo and Juliet as both a product of fate and of personal choices. On the one hand, Romeo and Juliet were fated to die due to the fact that they were born to parents of warring families. However, the fact that the families were warring was a choice made and carried out by the family members. Not only that, Shakespeare makes it very clear that both Romeo and Juliet had fatal character flaws of being impulsive.
While the play opens by referring to the two "star-cross'd lovers" born of two enemy households, we soon learn that the Prince holds the households responsible for continuing the feud and is now threatening the families with death should they continue. Not only that, even Capulet declares that men his and Montagues' age should be able to keep the peace in the city, showing us that even he is beginning to feel some blame for what is taking place, as we see in his line, "[A]nd 'tis not hard, I think, / For men so old as we to keep the peace" (I.ii.2-3). Therefore, while Romeo and Juliet were born to ill fate due to their parentage, it is their parents who have chosen to continue the feud, making them ultimately responsible for their deaths, as we see the Prince assert in the final scene of the play, declaring, "Capulet, Montage[Montague], / See what a scourge is laid upon your hate ... All are punish'd" (V.iii.302-303, 306).
However, Romeo and Juliet, themselves, are not portrayed as completely blameless. Both are portrayed as very stubborn and impulsive. Had they conducted their relationship with a little less haste and a lot more reason, they may have remained alive. Most importantly, had Romeo used his rationality to ascertain that the reason why Juliet's cheeks and lips still looked rosy in her tomb was because she was not yet actually dead, instead of allowing his emotions to govern him, Friar Laurence's final plan may have actually worked out, and the couple may have continued living.