Is the brother entitled to reclaim a piece of land he bought for his deceased brother, which is now registered in the latter's name, or should it be divided according to Sharia among his heirs?

The question is general, and according to its apparent meaning, the brother does not have the right to reclaim the land. If he bought it as a guardian, custodian, or agent for the younger brother, then the latter owned it, and upon his death, it transfers to his heirs. The purchasing brother's current action is an action concerning the property of the heirs. If he gifted it to his younger brother and a valid possession occurred, then he has no right to reclaim it, and the land is the property of the heirs. Issues of dispute and litigation are decided in the Sharia (definition) courts.