There are four types of marriages: monogamy, polygyny (polygymy), polyandry, and group marriage. Monogamy is one wife, one husband. Polygyny is one husband, several wives. Polyandry is one wife, several husbands. Group marriage is by far the rarest and has never been the prevailing form of marriage in any known society.
I dont know if you would call it group marriage but in some sections of our society a girl married in a family is common wife of all members of all male members. The reasons are strange but not unreal, by the way the area where Hastinapur was supposed to be situated around NCR area.
And if you think that group marriage means that everyone in the group is married to everyone else in the group; can be described as "poly polygamous" but can not be called polygamy really