She can move husband can't force her to stay. Husband can try to compel her to get back at his house only through court by filing rcr petition but the same doesn't work for harassment. She can also claim maintenance for her and children from him under various laws

Till the twins obtain the age of 5, custody will not be given to the father. 
she can not be forced to live with husband.

the wife can not be forced to live, the law has been settled by the Hon’ble SC. 

regards

Yes, she can live separately by applying judicial separation this is not divorce but to husband and wife stay in the different house.

Wife can ask for alimony and maintenance under Indian Divorce Act and Section 125 CrPC.

Custody of children will remain with mother.

No she cannot be forced to live with him. She can move immediately with babies and agaisnt any resistance she can call the police.

Custody will stay with mother only dont worry. And as she comes to her parents than she can file police complaint agsisnt him of DV and petition for maintainance from parents palc.e

Husband cannot force wife to stay unless di order 

2) welfare of children is paramount consideration 

3) court would award you sole custody of children 

No worries about Custody of children and forced stay.

The mother is authorized legally to have the custody of breast feeding child exclusively with her till child attains the age of 5 years as per Hindu Law.

The wife can't be forced to stay with husband. If situation is unbearable then she may stay away from her husband without divorce. She has to file application for Judicial separation proceedings under section 10 of Hindu Marriage Act which is maintainable against the husband under Hindu Marriage Act 1955.

1. Divorce means breaking legal relationship between the husband and wife and thereafter they become stanrger in the eye of law and staying together does not attract any social or legal obligations.

2. Therefore do not agree on her demand of divorce and stay as usual.

3. She can file case under section 498A IPC if the torture increases.

4. Additionally she can file case of maintenance under PWDV Act as well.

- Legally her husband cannot force her live with him against her consent. 

- Further , the mother is the preferred custodial parent when the child is less than five years old. The opinion of a child who is over nine years old will be considered.

- Further , you should know that for your sister Divorce will be not a better result for her future. Hence, before taking Divorce decisions, she is having the following right and claims from her husband. 

1. As per law, A wife has the right to claim decent living standards and basic comforts of life from her husband. Hence for claiming the maintenance for her & child, she should file a petition under section 125 CrPc.

- Her husband is under legal obligation to provide the same to her at any cost, even he is working or not. 

2. Law entitles wives a basic right to reside in the matrimonial/ home, whether the house owned by her husband or his parents, a rented property or officially provided to him. 

- Hence, for claiming her residential right, medical expenses etc, and also for teaching a lesson to the family members of her husband, who subjected her torture & harassment, she should file a petition under the provisions of Domestic Violence Act.

3. As per the Supreme Court, A wife has complete ownership rights over all her Streedhan, the gifts and money given to her before and after marriage. The denial of Streedhan to the wife makes the husband and in-laws liable for criminal charges. 

- And further, if the husband or his family members subjected a woman to cruelty for the dowry demand, then they can be booked under Section 498-A.

- Your sister should lodge a written complaint against her husband & his family members, in the Women cell/Mahila Police, after mentioning all the details of torture & harassment. 

- The women cell firstly will try to reconcile between them, otherwise, they will lodge an FIR against all the person, who subjected your sister cruelty. 

- Further, if you don’t want to create problems for your sister’s husband, and proceed for divorce, then she can get divorce decree within a short period of time, after filing mutual divorce petition. 

Nobody can force any one to do or to abstain from doing which one is legally entitled to do or not to do.

1. No, the husband cannot force her, she can leave husbands house and can come to her mother's place along with the child also she can file the police complaint and proceed with the registration of FIR against him for harassment and abuse. The age of children is small and court grant custody of the child below 5 to mother for their better care and welfare. 

1. Your sister can file for judicial seperation from the competent court.

2. Otherwise let the couple opt for Mutual Consent Divorce through which assets, liabilities and custody of children can be resolved amicably.

Divorce allows a person to break free from an onerous marital relationship. But since marriage is not merely a contract but a very important societal institution. The law has an interest in protecting marriage, and not allowing it to be severed only by choice and on ordinary wear and tear.  Since society in countries like ours takes special interest in protecting it – In our country to get a divorce one needs to prove certain grounds for eg : cruelty/adultery/desertion etc.  Known as matrimonial offences.

The Supreme Court of India has consistently held that in deciding cases of child custody ‘the first and paramount consideration is the welfare and interest of the child and not the rights of the parents under a statute.  In a custody battle between estranged parents, a minor child, who has not completed five years of age, shall be allowed to remain with the mother Gender is not a consideration in deciding matters of child custody and guardianship.

Firs find out the real cause of differences or problems between them and then suggest a solution suitable to them . I can suggest you that better solution is amicably settlement .

Minor children will mandatorily stay with the mother, ask your sister to leave with both of them, moreover request you to go the spot, call woman police station and register a general diary and then bring your sister back with help of woman police station, details are herein: 

Women's Police Station
3065, 9th Main Road, Siddanna Layout, Thyagaraja Nagar, Basavanagudi, Bengaluru, Karnataka 560070,at Eight Zero Two Two Nine Four Three Two Five Zero

Dear Ma'am/Sir

According to law a wife can stay separately from her husband if she has "reasonable cause" to do so. Now this term is subjective and in order to prove that there is a sufficient cause, it is advisable that your sister collects all the evidences of cruelty inflicted upon by her husband. 

Therefore firstly advice your sister to Keep all the evidences safe with her. Save all the call recordings, messages, photos, medical reports, medical prescriptions, bills, gifts exchanged etc. The idea should be to collect everything in order to prove your case in future or counter the possible allegations against you. All these evidences will help her immensely in the court.

The husband will not succeed in forcing her to stay with him. Even if your sister is not able to prove the reasonable cause and he succeeds in obtaining a decree of restitution of conjugal rights. Your sister can still refuse to comply with the decree and at best her property can be attached by court. But try to avoid such situation as it will have collateral implications in respect of maintenance, alimony etc. And moreover, such situation will give her husband an additional ground to obtain divorce. 

The custody of children is usually given to mother if the children are less than 5 years old. in your case, as of now it is highly improbable that the custody of twin babies will go to the husband. However, after a few years this benefit would not remain and the decision of custody would depends on several factors like: Financial status of parent, wish of child (plays important role), morals of parent, atmosphere of the house/place where child will stay, ability of parent to take care of child, education of child etc. So as long as your sister satisfies the court that all these aspects are taken care of and that she is a better person than the father to take care of children, they will stay with her.  

Hope this answer helps.

Best wishes.

She can ofcourse move put with the babies without divorce and custody papers.

Divorce can be filed after leaving the house. 

Babies are 5 months old so the custody will remain with the mother 

1. She is free to move out.

2. She cannot be forced to stay with him before divorce.

3. Petition for declaration of guardianship and child custody can be filed by her. Mother is the natural guardian of child as long as he is under the age of 5 years. Hence, the courts inevitably choose mother over father so far as grant of custody of a child under 5 is concerned unless there is insurmountable evidence to show that mother's conduct qua child is unbecoming of a mother.

she can stay separately without divorce. 

Under secular law as well as Hindu lawThe mother usually gets custody of the minor child, under the age of five. 

Your sister an opt to stay away from her husband even without filing the divorce case.

She cannot be forced by him to live with him against her willingness.

She can take the help of police if he forces her or tortures her in this regard.

She can have the children in her care and custody till they turn 5 years old and after that let the court decide the custody.

You can take her back to our home, he cannot stop her from leaving the house.

1. No husband cannot force his wife to stay with him even if divorce is not filed. 

2. No she doesn't have to giveup custody of any of her children to her husband in case of divorce because at this tender age children need their mother more than their father.