Bonded By Fire and Blood by Trina M. Lee

My fated mate and I are running out of time. The man who rejected me wants another chance, but before we can commit to anything, we have to evade the bounty hunters after us and find a way to keep from destroying one another.
Hex’s former bounty hunting coven has made catching Arsen and me their priority job. Our rare twin flame blood is in high demand among black market magic types. The bond we’ve forged gives us strength while also threatening to break under the pressure. Hex is doing what he can to help us stay balanced, but all he can do is try to buy us time.
All the time in the world won’t matter if the bounty hunters catch us in such a fragile state. Every night the darkness grows, slowly turning Arsen and me into killers without a conscience. Eventually we’ll turn on each other. We just can’t let that happen.