Justice for sister

My sister has been married for 13 years to an engineer in Riyadh and has two kids now a daughter aged 11+ years and a son 4+ years. Her marital life has not been sound since the beginning as that man holds a nasty attitude and has been always in practice of mentally torturing my sister by talking ill about her family members and humiliating her publicly and infront of his own family members too. He would constantly try to contaminate the minds of his kids too against their maternal relatives. He would miss no chance to humiliate all the members of our family and would try to provoke for retaliation. Their marital relationship had several hiccups during the entire period but she had to give up every time due to her kids. She joined as a teacher in a school to have respite from an abusive marriage. But then her husband stopped every kind of financial assistance and asked her to meet out her personal expenses from her own salary. A few days ago, he was talking to his daughter to snap her terms with all her maternal relatives and convincing her that they are very bad people. That made my sister lose her control and a fight broke out. He started uttering nonsense about my mother and other family members too. The man then asked my sister to leave his house and threatened to divorce her. He called up my brother who too lives in Riyadh, to come and take away his sister. When he called him for the second time, my brother reached over and enquired about the matter. He started provoking my brother by talking ill about my sister and our mother too. It eventually turned into a physical fight between my brother and sister’s husband. My sister pushed away my brother and urged him to leave and come later to pick her up. Her husband instantly called his two brothers who also live in Riyadh telling that his wife’s brother has beaten him up and they should come to take revenge. They both came over and started abusing and threatening my sister. At that very moment my brother came to take my sister and all three of them attacked him and even tried to kill using a piece of broken glass of the table. My brother somehow managed to escape with sister and her two kids and approached the police. But police after calling up my sister’s husband there suggested either going for a mutual settlement or terminating the marriage. My brother has brought my sister and her kids to Mumbai yesterday where the other brother and my mother live. After all this mishap we don’t find any possibility for that marital bond to continue any further. Please advice as how to seek legal support to give justice to my sister and plan her life ahead with two kids. She has all the things furniture and other items and jewellery etc. received as dowry lying at her in laws place in Aligarh (U.P.) but fears to come down to Aligarh as has been threatened by her brother in laws in Riyadh to meet very bad consequences if tries to come to Aligarh. Her husband would be coming over to Aligarh on 20th July, 2015. Can we file a case to claim for maintenance and custody for her and the kids? Is it possible to punish that man by holding him up in India and make him lose his job in Riyadh when he comes over after a few days? Can his brother too be punished for causing harassment to my sister and attempting to kill my brother? We have no proof as such to establish the cruelty and mental harassment inflicted on my sister by that man except her kids having witnessed all that.