Dowry threat from wife

My brothers wife married last year in April, gone to her home willingly with his brother, who has come to took her for family function, with jwellery & other belongings and now threatning us via filing a dowry case against our family including me, my wife, mom, father, brother & sister as well. Yesterday we got a phone call from family court & they ask us to come for a prior meeting (next week) at Seating centre in Aligarh(U.P), we are living in Delhi. We came to know that She has filed a complaint/FIR on 26th of Oct against our family including Our SISTER who has GOT MARRIED on 19th Nov 2018. 307, 498, and 2 other IPC are used against us in complaint. We are called on 20th Dec to meet at Seating centre via phone call. (Nothing recieved in writing) Suggestions Required? 1. What should be the first step? And how to proceed with this further. 2. Priority is to keep our younger siter (married recently) away from all this, how to do so? 3. Should we all go to the Seating Centre in Aligarh on 20th Dec or not? 4. Is there any real threat ? Even if they dont have any firm/stronger evidence against us? 5. Lawyer Recommendation for the same.