Am I entitled to claim a share of the house that my brother built on land he bought, knowing that he sold the land I inherited while I was a minor, and that I now live in it with my brother's children? And would my request for a sum of money to buy land and build my own house be considered an injustice to them?

Claiming a right is not injustice; rather, injustice is preventing the rightful owner from their right. The questioner has a legitimate right to their father's inheritance, like the rest of the heirs. It is not permissible to sell an orphan's property except out of necessity (such as the need for sustenance) or for a clear advantage (such as when the property is offered for more than its value). It is not possible to rule on the sale of the questioner's share of the land without knowing the reason and the role of the seller. Inheritance and joint rights cases must be brought before the Sharia courts for adjudication and for rights to be delivered to their rightful owners. A written fatwa is insufficient for such complex cases.