"Wherefore art thou Romeo"

Juliet is asking, really, why fate has separated her from Romeo - or, at least made their love so doomed. It is a rhetorical question. She is railing against fate.

The families are at war - so Juliet knows herparents will not let her be with Romeo, because he comes from the opposing folk.

Really, she ought to be asking why is he a Montague, since it is presumably his surname, and hence parentage, which is the issue - not that his name is Romeo! Lol.

Juliet's family (Capulets) and Romeo's family (Montagues) are in a bitter feud. Their families hate each other and fight at the slightest provocation. Juliet is sad because this boy she met and likes has the wrong name.

Wherefore art thou Romeo? means

WHY did you have to be Romeo, a Montague, who I must not love?

She then goes on to say

Deny thy father and refuse thy name, or, if thou wilt not, be but sworn my love and I'll no longer be a Capulet.

which is to say, I wish one or the other of us had a different name- If you won't quit being my enemy, I'll quit being yours.

She goes on a few lines later to point out

What's in a name? A rose by any other name would smell as sweet.

In other words, isn't it frustrating that a little thing like our family names should mean so much and keep us apart.

Okay I get it now. I knew while I was in school I could have paid more attention in class, I never knew how bad I was! All this time I thought Juliet was on the balcony just asking, Where's Romeo? *lol* Thanks for enlightening my sorry excuse for a brain hehe.