How could one of the most powerful vampires on this earth be taken and held against his will?

I was captured, tortured, and held captive until I feared I would go mad.
Then he brought her to me, tempting me with the taste of her blood.

Our souls call out to each other bounding us for all eternity.
Only death can separate us.

I don't care who you are touch what belongs to me
and I will wipe you from the face of this earth.

How can I be his when he's betrothed to another?
My heart has been torn out of my chest and
stamped on so many times leaving me broken
and yet my soul still yearns for his.