without divorce second marriage is possible according to law

Hello i have to ask something my father is married with my mom in 1979 and my mom is first wife of my father but my father have affair with another lady also we are onr brother and sister in 2001 my father married to that second lady in without gave divorce to my mom which we dont know we thought she is living just like that with my father in another house but know in 2017 my father is died in december and after that that second lady starting greedyness and asking for the legal rights in property she is asking to share in property and giving trouble to us pls suggest anynone is she have rights we dont know b4 that she is married to my father but know she is telling to everyone that we got married i have photos and certificates but how it is possible that she is married with my father if my mom not gave a divorce to.my father in whole life she is giving so much trouble to us she dont have any cgild pls give any suggestion anybone pls

Hello i have to ask something my father is married with my mom in 1979 and my mom is first wife of my father but my father have affair with another lady also we are onr brother and sister in 2001 my father married to that second lady in without gave divorce to my mom which we dont know we thought she is living just like that with my father in another house but know in 2017 my father is died in december and after that that second lady starting greedyness and asking for the legal rights in property she is asking to share in property and giving trouble to us pls suggest anynone is she have rights we dont know b4 that she is married to my father but know she is telling to everyone that we got married i have photos and certificates but how it is possible that she is married with my father if my mom not gave a divorce to.my father in whole life she is giving so much trouble to us she dont have any cgild pls give any suggestion anybone pls