I don't think that's possible

The tragic ending of Romeo and Juliet is tragically, I can't denial that. But I don't think the prince can do anything to stop another tragidy like this. First of all,most people never completly realize their mistake unless they've lost their most precious thing of their life,you hardly can pull someone out of their misrable personality by violence and criticize,so I would suggest the prince just stand aside and see what they will become in the future,because I don't think telling people what's good and wrong is human's responsibility,the only way they would realize their mistake is suffered from their own consequences.