A Fairy Tale

Do you know, the story of Alice and Jack?
It is this:
Yahn, with a heart full of cotton and candy, fell in love with a princess. She had wide, soft eyes, the colour of chocolate. Her hair fell in silky tendrils to her elbows. Her smile lit up the sky.
Jack knew all this.
He watched Yahn and the princess grow up together.
Over time, Jack played his hand.
The princess and Yahn would steal moments:
in dusk, in bedrooms, in store rooms.
Innocently.
Jack waited.
One night: he asked the princess to a fairy tale dinner. She accepted.
Four years later: and no one is happy.
The princess and Yahn love one another.
But they both love Jack. And Jack loves them both.
What to do? What to do with this heart split thrice?
Jack keeps the princess close. But she steals away from under his fingertips, and slips through the open windows of nighttime. Yahn welcomes her, gently, gathering her melted chocolate eyes and hair of silk.
Jack, outside, knows this. His heart cracks a little more, crumbles a little further, til what is left is bitter and broken. He has made his choice, and now he will pay his dues.
He cannot name what it is that makes him stay. It is a formless void, a slate of murky grey. It has neither name, nor form, but a great deal of persuasion. It is the most dangerous kind of Thing.
To Jack, it is the black dog that stalks his dreams.

Is Jack the prince? Or is it Yahn, with his fingertips of sky?

And as for the princess: why so indecisive? What makes her stay?

What am I missing?
There is something here that I am failing to grasp.
There is a link that I do not yet see.

A Fact of Relevance
Jack, if he knew I wrote these words, would strangle me and leave me to die, in the cool puddle of a gutter drain.