Does the brother have the right to claim ownership of half of the agricultural land he has been working for 15 years in exchange for half of the income, knowing that the land belongs to the questioning brother and there was no prior agreement on ownership?

If the lease agreement stipulates that the brother works the land in exchange for half of its produce, then this lease is permissible according to the majority of jurists. The brother has no right to demand ownership of half of the land; he is only entitled to the agreed-upon wage. His demand for anything beyond that is invalid and constitutes consuming wealth unjustly, which is forbidden by the Almighty's saying: "And do not consume your properties among yourselves unjustly."