Bigamy, or having two partners, is rather common among Hvetshran that live in a clan. Urban Hvetshran or wanderers seldom practice bigamy. In the case of the first, he or she mostly adapted to human behavior; as for the latter, this is because it's practically impossible doing so in the wild.
Why is it that Hvetshran find it natural to have two partners? Probably the main reason is because Hvetshran find it easier and faster to reproduce with two partners. In the case of a male having two wives, this is obvious as they would be able to get pregnant simultaneously. However, in the case of a female having two husbands, the reproduction speed will also be slightly increased, as for instance the sperm quality will not decrease due to excessive intercourse.
Apart from the need for reproduction, there is also a reason within the social dynamics within a clan: staying without partner gives off a disgraceful vibe within Hvetshran society. Therefore, if there are more females or males within a clan, it is only logical that the so-called 'outnumbered' gender will tend to have two wives or husbands.
A third reason would be the toleration for other sexual affinities: when a Hvetshran is noted bisexual and has the chance to do so, he or she regularly takes two partners of different gender. A homosexual individual often takes two partners as well, if possible, because they still feel the need to reproduce - if not for himself or herself, then he or she does so for the clan.
The last reason would be that having two partners shows that the individual is strong and has influence within the clan. This idea is often supported by the clan, as it increases the chance his or her children will also be strong and therefore create a strong next generation.
Since it is taboo for a Hvetshran to propose to join in an already existing marriage, the agreement to marry two people should either be made before partnership between them has been made official, or he or she should be the party receiving the marriage proposal.