X could not survive without Y. 

And without X, Y would die.

No matter how much X may lie

And Y is such a bad guy,

Both knew they'd continue to try.

Because both had goals, wished to fly,

To cross their hearts, hope to die,

While the other was standing by,

They'd endure fights, every sigh.

So, the knot, they agreed to tie.

But,

They wanted no love to grow dry.

They wanted no cause to cry,

No need to fret, wonder, or pry.

No contemplating, no "why?".

So, in death, they said, "Good-bye."