I'm seriously considering having my two protagonists decide "you're the one for me" pretty early on and actually stick with it throughout the book. Of course, there will be roadblocks, including possible execution for treason and him being practically dragged to the altar to marry someone else, throughout. But, they're together, and decide to be together probably in the first 1/3 of the book and actually make it.

I'm just wondering if that's a death sentence for the book, or is the lack of a 3rd character to woo her away with "real romance" enough of a twist in a young adult novel in this day and age... (That's right, a YA novel without the love triangle. He does have a girl in love with him, but it's unrequited and never goes anywhere except politically)

There's just a lot to go on elsewhere. The romance isn't the main plot, but it does play a key role.