is an anthropological
term denoting consanguinial kin
who are in the same descent group
as the subject and are from the parent's same-sexed sibling. A cross cousin
is from the parent's opposite-sexed sibling. Simply put, a parallel cousin is a first cousin
who is the child of the father's brother (paternal uncle's child) or the mother's sister (maternal aunt's child), while a cross cousin is the child of the mother's brother (maternal uncle's child) or of the father's sister (paternal aunt's child).
The role of cross cousins is especially important in some cultures (such as the Iroquois system and among Hindu where marriage is promoted between them and the subject (ego). Parallel cousins, on the other hand, are usually not the subject of promoted marriage since a union in many cultures would fall under an incest taboo. In a patrilineage, parallel cousins are part of the subject's (ego's) unilineage whereas cross cousins are not. The same is true in matrilineal societies, wherein parallel cousins are considered to be related to the subject (and therefore unwedable) while cross cousins are not.
In many societies parallel cousins use names that we often associate only with direct siblings. For instance, in the Omaha system
, a male parallel cousin is referred to as "brother". Likewise, a female parallel cousin is "sister." This system is also in place in the Crow system
, the Iroquois system
and the Tamil
system. The Hawaiian system
is different in that they apply sibling naming terminology to cross cousins as well. This system is not in use in the Eskimo system
, nor in the Sudanese system
as they have separate terminology for cross and parallel cousins.
John Maynard Smith
), in "The Evolution of Sex"
notes that Richard D. Alexander
suggested that paternity uncertainty may help account for the intermarriage taboo
on parallel, but not on cross cousins
. Fathers who are also brothers may overtly or covertly share sexual access to the wife of one or the other, raising the possibility that apparent parallel-cousins are actually half-siblings, sired by the same father. Likewise, mothers who are also sisters may overtly or covertly share sexual relations with a single man, raising the possibility that apparent parallel cousins are actually 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 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 Ego's mother had a brother, and Ego's father impregnated his wife, thereby allowing apparent cross-cousins to be covert half-siblings, sharing the same father.