Since this property is in your mother's name though you and your brother constructed structures over it on your own expenses, it shall be considered as your mother's property only.
For an indisputable settlement, your mother can transfer the property to both of you by executing a registered family settlement deed in your favor on the basis of the each floors occupies each other keeping the roof rights and other area outside the structure as common with equal rights for both.
She can also mention that since her daughters has been gifted with properties and movables they do not have any rights in this property now being transferred to your names by registered settlement deed.