mental harassment from relatives and cousin sister

please read this completely and give me advise.

when i was in my college studies my cousin sister is my juniour , she is very close because she is my relative and relation is sister relation. one day she told me rumors are spreaded in the class , that she have a love affair with his class mate. and she requested me to talk with those boys, next day she introduced her classmates and i asked those boys, they told all are rumors. i also convinced my sister sometimes some rumors will spread so dont worry. after one year really love affairs started , eventhough i was senior batch student in the same college i dont know. after that her mom and father asked me. I told i dont know abt love affairs, but last year this rumors incident happend.
after that my cousin sister parents and relatives forced me to enquire abt that boy whether he is good or bad, when i asked his class mates they told that boy is having bad habits, that same thing i told with my cousin sister parents and relatives.

after that her marriage is settled with that same boy,

after that my cousin sister and his friends told me to call that boy, and given the phone number for this i dont have any proofs. i called and i told bithday wishes.

after that my cousin sister told with his parents and relatives i was trying to spoil her marriage and she created so many dirty stories on me. and finally all my reltives and her parents extremely insulted me and my parents with extreme dirty words. nearly 35 people nearly 8 hours they insulted.

i requested all the people from my side no mistake and they did not believed my words. one side i accepted i called to that boy.

because of that quarrell my brother, sister, father and mother also extremy insulted me and extremely suspected my character.

after that my cousin sister and her lover and her lover friends created one email with my name and they created one letter and they told to my cousin sister mother. but they did not speak abt that email letter in the quarrel.

finally i was the person who insulted in the society. and for my parents also it is extreme harassment.

this incident happened 6 years back.

know my cousin sister and her husband(he is lover ) doing black mailing with that created e mail.

after that i have some evidences, regarding this issues which are favour to me to proove my self.

know is there any chance to go legally on my cousin sister and her husand on this.

Pls give me advice