Polygamy and incest go hand and hand. It is taught in their doctrines that incest is a sacred act. So sacred, in fact, that it is not to be discussed with 'outsiders'. The founders of Polygamist Mormons taught incest 'way back when' and still do today.
Below you will find several first hand accounts of incest in Polygamist families and forced marriage to close relatives. Unfortunately these are not isolated incidences as the original teachings are still practiced to this very day.