Did your mother make a will during her life time? Was a deed of settlement respecting this property made between you and your brother whereby your brother was allowed to construct an apartment thereon? Did your mother during her life time authorize your brother to raise a construction on the property after dismantling the same? When did your brother construct the apartment? If the property has been inherited then it belongs equally to you and your brother. As such, your brother could not have made a construction without your express sanction.
You can proceed to issue a lawyer's notice to your brother and then follow it up by filing a case for property division in the court to cull out your share therein.
