Permanent injunction

As the property's legal owner through a gift deed, you have certain rights over its usage. Filing a suit of permanent injunction against your brother and his wife is possible under the Specific Relief Act, seeking to prevent their entry onto your property. The act protects your possession rights and restricts their entry without lawful authority.

However, their legal remedies could involve challenging the injunction by asserting their right to reside if they can prove any prior agreements, tenancy rights, or familial arrangements allowing their stay. If they've contributed financially or if any promise was made for their accommodation, it could affect the case's outcome.

The case of Ram Sumer Puri Mahant vs State of UP and Ors. established that if an individual's possession is lawful and based on consent, injunctions might not be granted without due process. Therefore, your brother and his wife might argue for their right to stay based on prior arrangements, which could impact the court's decision.

Consulting a legal expert for tailored advice considering all relevant aspects of the situation would be crucial before taking legal action.

If you do not want them to be in the house again but they still insist on coming to your house despite asking them not to, then you can file a suit for injunciton to restrain them from interfering in your peaceful possession and enjoyment of the same

As your brother and his wife are stated to be living separate since their marriage, there is no cause of action against them, hence no case is made out which may survive to restrain them from entering the house gifted to you.

SImply tell them to 

They have not contributed financially. The said property was a gift to my mother from her father (i.e. my maternal grandfather at the time of my mother's marriage). which was eventually gifted to me this year by my mother.