▁ ▁The ▁most ▁common ▁form ▁of ▁group ▁marriage ▁appears ▁to ▁be ▁a ▁tri ad ▁of ▁two ▁women ▁and ▁one ▁man , ▁or ▁less ▁often ▁two ▁men ▁and ▁one ▁woman . ▁There ▁are ▁also ▁poly f idel it ous ▁families ▁formed ▁by ▁two ▁heter osex ual ▁cou ples ▁who ▁become ▁a ▁f ours ome ▁and ▁live ▁together ▁as ▁a ▁family . ▁ ▁Leg al ▁aspects ▁ ▁In ▁most ▁countries , ▁it ▁is ▁not ▁explicitly ▁illegal ▁for ▁three ▁or ▁more ▁people ▁to ▁form ▁and ▁share ▁a ▁sexual ▁relationship ▁( subject ▁sometimes ▁to ▁laws ▁against ▁hom osex ual ity ), ▁though ▁such ▁rel ational ▁forms ▁risk ▁running ▁af oul ▁of ▁state ▁or ▁local ▁ordin ances ▁b anning ▁un mar ried ▁coh ab itation . ▁No ▁Western ▁country ▁perm its ▁stat ut ory ▁marriage ▁between ▁more ▁than ▁two ▁people . ▁Nor ▁do ▁they ▁give ▁strong ▁and ▁equal ▁legal ▁protection ▁( e . g ., ▁of ▁rights ▁rel ating ▁to ▁children ) ▁to ▁non - mar ried ▁partners ▁— ▁the ▁legal ▁regime ▁is ▁not ▁compar able ▁to ▁that ▁applied ▁to ▁married ▁cou ples . ▁Ind ividual s ▁involved ▁in ▁poly am orous ▁relationships ▁are ▁considered ▁by ▁the ▁law ▁to ▁be ▁no ▁different ▁from ▁people ▁who ▁live ▁together ▁or ▁date ▁under ▁other ▁circumstances . ▁ ▁Non - Europe an ▁cult ures ▁Among ▁the ▁An cient ▁Hawai ians , ▁the ▁relationship ▁of ▁pun al ua ▁involved ▁" the ▁fact ▁that ▁two ▁or ▁more ▁brothers ▁with ▁their ▁w ives , ▁or ▁two ▁or ▁more ▁sister s ▁with ▁their ▁hus b ands