Visitation Hindered by Spouse' kin

I am a 39-year-old man married for the last 14 years , I have been living alone for the last 3 years as I used to drink heavily earlier. Since then I have undergone rehabilitation and have been sober for the last 2years. I work at an MNC . My wife during my absence (while in rehab) returned to her mother's house along with my children and began working as an assistant nurse to support herself. Even from my days at the rehab and post my discharge from there I have been regularly supporting my wife and children financially. Now the problem my wife keeps my meeting with my children or herself a secret as she would not want to offend her Mother and Older brother. She feels threatened that they may stop speaking to her and if I did ever relapse then they would not support her. Meanwhile, I have come to find out that my wife's mother makes my 11year old daughter do housework (washing vessels of 6 people ) sweeping etc. and Son who is 13 is asked to go the bazaar etc.My wife does not allow me to meet my children and keeps it a secret fearing dire consequence from her brother who happens to be an alcoholic and violent individual, I seek advice to have my family back with me, please help