When distributing stock profits, do they belong to me alone, or should they be distributed according to the proportion of my contribution and my brother's contribution to the purchase of the stocks?

The profits resulting from the loan belong solely to the borrower, because the loan transfers to the ownership of the borrower and becomes his liability, and he is obligated to repay its equivalent. It is permissible for the borrower to give his brother something from these profits upon repayment, without any prior condition, as this is an act of good repayment.