relations with the wife of one or the other, raising the possibility that apparent parallel cousins are in fact half-siblings, sired by the same father. Likewise, mothers who are also sisters may overtly or covertly share sexual access to the husband of one or the other, raising the possibility that apparent parallel cousins are in fact half-siblings, sired by the same father. Note that there is no possibility of any classificatory cousins sharing the same mother. Because maternal identity is (almost) never in question, they would be automatically classified as siblings. Only mistaken paternity leads to such errors. This possibility is much less likely for cross-cousins, because in the absence of full-sibling incest, it is unlikely that cross-cousins can share a father by overt or covert sexual relationships. It would only be possible if a subject's mother had a brother whose wife was impregnated by the subject's father, thereby allowing apparent cross-cousins to be covert half-siblings, sharing the same father. Middle Eastern parallel cousin marriage Andrey Korotayev claimed that Islamization was a strong and significant predictor of parallel cousin (father's brother's daughter – FBD) marriage. He has shown that while there is a clear functional connection between Islam and FBD marriage, the prescription to marry a FBD does not appear to be sufficient to persuade people to marry thus, even if the marriage brings with it economic advantages. According to Korotayev, a systematic acceptance of parallel cousin marriage took place when Islamization occurred together with Arabization. See also Kinship and descent Family Genealogy Cultural anthropology Cousin marriage List of coupled cousins Mahram Notes External links Kin Naming Systems part 1 and part 2 at Palomar College. Matrilineal and Patrilineal Kin at the University of Manitoba. Cousinship