1. you need not worry
2. you must appear before the Magistrate on the date mentioned in the Summons
3. you have to inform the court that your are the legal heir of original owner and that you are not in occupation or possession of the property presently. Also that the flat which you have in the building is lying locked since a long time
4. you need to say that the property is in control of your cousins and so you are not aware about the dealings with the property with regard to the offences which are mentioned in the summons
5. it seems that someone has lodged a complaint against the landlord of the building for letting dirty water or sewage from the drain pipes in the building which is a cause of nuisance
6. you just have to inform the court that there are property disputes between you and the other legal heirs and you are not in control of the property and also your flat is locked, so you are absolutely not aware who is letting the dirty water to drain from the sewage pipes
7. you have to tell the court that BMC issued the notice without even investigating as to who was responsible for letting the dirty water to be drained and has sought to made the landlord liable