Father Property given to brother

Hi This is regarding my father property which was built by him . After the death of my father the property was transferred to my mother name on the basis of his will in 2011. As per his will all rights has passed on to my mother. Now my mother has tranferred that property to my elder brother name without informing us. Now the registery has also done and house tax is also on his name. Kindly suggest how we can get our share we are three brother and one sister. Our mom is still alive . Thanks