Firslty, you need to get the legal heir certificate for claiming any right over the property.
Secondly, you may have to apply for the same in the Civil Court whcih May take 2 or 3 months.
Thirdly, once you get that then you can apply for your share in her property under the Hindu Succession Act.
Fourthly, you may be asked by the court to show that your mother married to him.
Fifthly, once you are able to that then the property may come to you as per the Hindu Succession Act.
But, your brother would also have share in it.