False cheque bounce

My brother has borrowed some money from a financier.it was about 1 lakh 60 thousand and 70 thousand from his wife.financer belongs to a political party.my brother gave a cheque as a security.my brother continues to pay interest from a long time.but failed to pay the interest for some time.financer son is a powerful and has criminal records.his son n they both keep us mental torcher by calling us and also by visiting our home.my brother has a friend from whom we had some money which we had given to him.financer son has taken 1 lakh 85 thousand from him.but his mom n dad said we don't know about any money.my brother friend does not want to include in this matter due to the political relations of the financer family.we continue say to them that u take ur 45000 n do some compromise with us.but after a long time they call is that they agree to us so me and my sister visit their house alone.but there they said they don't want to talk to us so they call my brother and then they signed forcefully the cheque that was given as a security of 5 lakh by my brother and they send a legal notice by an advocate to us.now we are very confused that what should we do.