Houses are not haunted. We are haunted, and regardless of the architecture with which we surround ourselves, our ghosts stay with us until we ourselves are ghosts.
Hauntlings are creatures born with a close connection to the undead, particularly those of a ghostly nature. The true origin of the race is unknown, but many scholars have theories on what causes these strange abnormalities. The most widely excepted theory involves the idea that ghosts somehow force themselves into the womb of a pregnant creature, replacing the soul that would inhabit the fetus and thus being born. Others believe that these creatures are born from residual energy from poorly cast resurrection spells remaining in the mother and passing on to the unborn baby. The last theory, and one often dismissed by those who study such things, is that the Hauntling is the offspring of a woman attacked by an undead while pregnant. Interestingly, this is the most common origin belief among commoners.