In the novel The Succubus Gift, the Telepathic Clans are descendants of an ancient people who once ruled Northern Europe. Genetically, they can interbreed with humans, but they are also quite distinct. The Gifts are not evenly distributed, over fifty percent of telepaths have only one gift, Telepathy.
In Ireland the oldest people are remembered as the Tuatha de Danaan, the People of the Mounds. In their ancient language the word for Tuatha, or People, was Clan. When the first Gaels, the sons of Mil, arrived in Ireland, they found the Tuatha De Danaan, the people of the Goddess, in control of the land.