Escape to Creeporia - Blood Brothers, #1

Two of the world's top assassins-fraternal twins separated from birth, but inevitably drawn to the same kind of women-find themselves married to a pair of sorceresses. When their firm schedules the hit men for cancellation, the brothers' one escape is through the women they love into a realm of magic, dragons, and warlocks, which will require both the assassins' and the sorceresses' skills to survive.