Polygamy

Genosism doesn't explicitly forbid it, but it isn't really a part of any of the Western Voscan cultures, with the exception of the Ohanedin of Iber. The Ohanedin see it as perfectly natural (probably because the men of their society regularly suffer considerable attrition) and generally four or five women share one husband, with the number rising as the individual rises in status.
The one crime which carries the punishment of death in an Ohanedin society is murdering a member of your own family. An easy way to prevent powerful women from scheming against each other is to marry them off to the same man, or to brothers, etc. This theoretically prevents potential conflict between them by technically making them into the same household. Needless to say this doesn't actually work.