I first heard about the concept early on in my research, when I met with a former Episcopal pastor who was working as a car salesman in Maryland. He told me that for much of his life he'd had enormous difficulty sustaining personal commitments.
"I'd gone through some really tough times, broken vows, broken promises, a sense of never being in charge of my life," he said. "At times it was terrible. During the first few months of my marriage it was if there were three of us in bed--my wife, myself, and some Evil Presence. [Healing the Family Tree by Kenneth McAll] opened my eyes; it helped me resolve these conflicts. I learned that an entire family line can be cursed by demons. Somehow this evil gets into the family, and then it's passed on generationally. Generation after generation is contaminated by it, unless steps are taken to break the curse, to purify the familial lineage."
Someone should write a work of IF based on that idea.