Divorce Notice issued during living family

Dear Sir, I'm Vaitheeswaran aged 40 years old bachelor. I live with my Mother, 3 elders in which my eldest sister is married, a divorced sister and unmarried sister. My family is dependent on me. Now the issue is my eldest sister was married to my uncle 22 years back and has a 21 years old daughter doing B.Com. My uncle does lavish expenses and does not care about family neither wife nor daughter. My uncle doesn’t give the salary properly and however managed to run the family past 22 years. The issue started here that sister's daughter fell in love with a guy and started to created problems with my sister but my uncle supported her irrespective of her choice for marriage as he doesn’t want to spare money for marriage expenses nor marriage jewels which was saved by my sister from the uncle salary. My sister advised her daughter that to concentrate in the studies and after studies that she can choose her choice for marriage. My sister extended one step and beaten her daughter as whenever her daughter quarrels with my sister for marriage during the B.Com studies. Even I advised my sister daughter and uncle, but they didn’t cared about it. Now the problems grown to the extent that my sister's daughter also started to beat my sister very harshly which was supported by my uncle. Last week my sister came to my home to see my mother as mother had angioplasty surgery 5 months back. My uncle dropped my sister at the railway station to reach my house. After that Yesterday my sister received a notice from my uncle which are as follows and given in short: 1) My sister spent her husband earned jewels (which was saved from lavish expenses) for mother angioplasty surgery. But the truth was we sold our jewels of my mother, other two sisters jewels for my mother’s surgery expenses. 2) I lost my job 2012 and started my browsing centre business with my mother's jewel sold out money. But my sister husband says that my sister gave her jewels for my business. 3) Above all this, they say that my sister was planning to marry her daughter to me. But this not true. I and my sister have no such plan. I’m a 40 year old person and waiting to get my other elder sister married first then later I can marry a girl but not my sister daughter as we treated her our family daughter. 4) My sister daughter complains that I asked to do DNA test and blood relationship which we didn’t say them. 5) My sister husband says that the sister pressures her daughter to marry me else she will poison her daughter. But which was not true. Now stating all the above points, my uncle forces my sister to give divorce acceptance within 15 days. My sister is ready to compromise this situation as my sister wants to safeguard her daughter as my uncle is undependable that he may ruin the life of sister and daughter. I request you to give your reply at the earliest. Regards M.Vaitheeswaran