Cheat by cousine

Respected sir/madam i am a married woman.12years before i had marriage. i have two children.before my marriage i was cheat by my cousine brother. as we were going frequently to his house he and his brother took some photos of mine.than he started blackmailing me.he told me he will give only if i spand one night.otherwise he will show to all.i was disagree because he was smaller than me.i was nearly 25years and he was in class 12.but finally i had no option as they were very rich and all laws and police were in their hand.i asked his mother also but i did not get any response.than i agree and also i got some photos back.after that i got marriage.he and his family attend my marrige.after marriage i came to month after they also came to my house and again he started blackmailing me.again he was asking the same thing. i stopped him.that time my husband was in germanny, after one month i also went .one day he sand me mail writting all slag languages.than my husband came to know all.after coming back again he started blackmailing parents and my husband came to know and also asked me to inform his parents. i informed his parents.his parents gave me assurance that hereafter he will not call you.soafter he did not call me.but now also am very scared about him and his family. so my husband is asking to turn off the relation. but i feel that if i turn off they will take some legal action to spoil my family.because may be he kept some photos with at this point if he or his parentns do something what i can do.please help me.wheather i can do manhani mamla and cheating case against husbend and my in laws opinion are sufficient to prove him.he spoiled my marriage life. my husband does not behave properly with me,but we are still together because of children.sometime i feel that i did big mistake and for that i will get punishment.but my question is wheather really i did any mistake.please give me answer.