how to determine customary practices

sir.. we both r hindus. both r Same cast sc. from  state. finally yesterday i marry a girl in arya samaj.they gave marriage certificate also. love marriage happened in arya samaz bcoz both side parents didnt agree for my marriage. bcoz of my girl friend is my fathers sisters daughters daughter. so geologically she is in daughter relationship to me. but we got married with the guidance of my lawyer. he said that my girl friend and my relationship is not there in prohibited list. and we r not sapindas also. so that we can marry. in the guidence of my lawyer we got married. but my girl friend parents file a case on me to break my marriage. they file case that as per custom in telangana state one shouldnt marry the above relationship. i didnt understand which law nd section nd in which book that custom rules are there.can u plz tel me the website link or book name that will give complete details about custom marriages in all states of india.wil court break my marriage