I had to change the question a bit. From "preferred," I went with "dominant" because I think that you are looking for the theme that is most present, one that could be more easily selected from Shakespeare's drama. I think that there are many themes that can be extracted from the play. The link below might help in this pursuit. I think that there is a very strong theme evident on the Capulet side of the drama. The intense gap that exists between Juliet and her parents might speak to the danger of what happens when parents do not listen or hear their children. In Act III, Sc. 5, the discussion that takes place is one that reflects parents seeking to enforce their will on their child. Shakespeare's exploration of the child and parent theme is not necessarily new. Yet, he does bring a new dimension to it in suggesting that if parents do not have a close connection to their children, enforcement of authority's desires upon them can only result in dangerous realities. The bond between parent and child is severed when this happens. This is a very powerful theme that I see in the drama and one that I find extremely compelling.