Are the father or brothers entitled to claim ownership of the son's money, given that the father had previously sent financial assistance to the son for a failing business project, and that the son subsequently started his own project and amassed his wealth through his own efforts?

The amount sent by the father (10,0 dinars) has three possibilities: It could be a loan that must be repaid even if the company incurs losses, or a partnership where the father bears the loss if the company loses, unless there was an act of transgression on your part, or a gift, which is unlikely. The expenditure on your siblings was not intended as a loan to be repaid, so you are not entitled to claim it back. You are wronged by your father and siblings' demands, and they are not considered partners in your wealth. The solution lies in reconciliation, satisfying your father, and being kind to your siblings. If that doesn't work, then resort to people of virtue or the Sharia court to resolve the dispute.