Polyandry is still practiced in parts of Tibet and around the regions of Dolpo and the border areas where there is a Tibetan speaking majority.  I have Tibetan friends who have 2 Dads (!!) and they do not know which one is their real father...The parents keep it a secret so that the kids' affections would not be biased towards them.

BTW, in medieval Tibet where fertile land was scarce (since most of Tibet is a desert), polyandry was practiced to keep the land from being split further.  A woman would get married to all the brothers in a household (with the youngest male sometimes not even a teen!).  Also, it was believed to bring the family closer leading to co-operation since it was an agrarian society, etc.  But did it really?  No one ever knows, at least not sexually.  I still wonder how these modern Pandavas do it.