Hello
1) If the property that was transferred to you by your father vide a Gift Deed was his self acquired one the transfer is absolute and as such it should not affect your rights/shares in the ancestral property. You may need to convince your father and tell your brother that he will land in legal trouble by coercing the old father to divide the property your legitimate rights.
2) The property gifted to you by your father does not qualify to be ancestral property as he had acquired the property himself and your can not make any claim as a right. In case you die without a Will your son will become entitled to a share in the property.