I differ with above advice, though it might appear safe to approach police station like suggested above, that will surely be the stepping stone ending of marital life, for the girl and he side it would always appear that your brother approached police when things could have been solved by mutual talks. Police station is meant for people who are on the wrong side of the law, thieves, murders, rowdy sheeters are best people suited to go to police station. What is the work of police between two grownup married people? Has the wife done dacoity, has the husband raped wife, has the husband gotten physical with wife, injuring her etc? No. Then there is no need for you people approaching police station.
Ask brother to keep visiting the wife as and when he can, let her stay at her parents house as long she wants, clearly there is a situation where both are not able to adjust with each other, IF you jump the gun and apply for divorce, the wife has many a way to torture you all legally by filing cases like 498a, DV, 125 crpc etc. So its wise to let the wife stay with her parents, and the husband keeps visiting the wife till they both develop understanding and come to a reasonable conclusion as to how to move ahead in life. In the meantime, you all as the immediate family can approach their family and try to solve this matter peacefully like responsible grown-ups. Remember its not just question of two lives, but the lives of people involved of both the families. Raising voice, shouting etc will only lead to fights, and a real visit to police station. Control your respective tongues.
I do not suggest filing for divorce, take some time, try various means to gel up together, then if all have been tried and still not able to get along with each other, only then think of filing divorce based on desertion. How to file for divorce? First send notice via lawyer, asking her to join husband in new town in the new flat, then if she refuses such in her reply, or does not respond at all, then can file divorce. Filing RCR directly is also advisable here, if she denies coming back to husband, then RCR will go in favor of husband and based on that when desertion is proved, can file divorce petition.
She claiming alimony, maintenance is all in the game.
My take on the query is, it better to follow trend, marrying was a wrong decision, live-in relationship is trend now. Its kind of mistake to marry these days, where patience are wafer thin and ego are big as elephant. Anyway, whats done is done, follow what I have advised above. Hope for the best.