the.com/polygamy

Marrying more than one spouse, because apparently one set of in-laws wasn't enough.

means The practice of having more than one spouse at the same time.

from From Greek polys, 'many,' plus gamos, 'marriage' — the same gamos that gives us 'monogamy' (one marriage) and 'bigamy' (two). The word traveled into English through Late Latin and French around the late 1500s, originally used to describe customs observed in other cultures before settling into its familiar legal and anthropological sense.

legal status
illegal in most of the world, legal in dozens of countries
etymology
greek for many marriages, practical to a fault
common form
polygyny, one husband, multiple wives, dominates historically
rare twin
polyandry, one wife, multiple husbands, far less common
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