The subsection system automatically prevents incest between siblings and any relatives closer than cousins. Cousins that are children of classificatory siblings (who may, by definition, also happen to be true siblings) of the same sex are themselves classificatory siblings, and may not marry; but children of classificatory siblings of the opposite sex are of the appropriate subsections for marriage, and marriage between so-called "cross cousins" is actually encouraged in traditional society. Where a couple are not merely classificatory cross-cousins but are true cross-cousins (i.e. their parents are actual siblings), marriage is generally frowned upon.