What is the legal ruling regarding the issue of a brother residing in his sister's renovated house being asked to pay rent or compensate her for the renovation costs after a contract was signed between them, and what is the definition of the oppressor and the oppressed in this case?

The aforementioned agreement is not considered a valid rental contract, due to the absence of a specified duration and a specified rent (which is the cost of repairs).

Your brother is obligated to pay a fair market rent for the period he resided in the house. He is entitled to reclaim what he spent on repairs, in addition to the supervision fee for those repairs.

If the fair market rent for the four years is not less than the amount he spent (80,0), along with his supervision fee, then do not demand the difference from him, out of consideration for brotherhood. However, if it is less, you can give him the difference in cash or allow him to reside in the house for a period equivalent to that difference.

Your brother has no right to reside in the house now except with your or your husband's consent, whether for rent or free of charge.

The advice is that if the fair market rent for the four years is not less than (80,0) along with his supervision fee, then refrain from demanding the difference from him, out of consideration for brotherhood and kinship. If the fair market rent for the four years is less than what he paid, then either give him the difference in cash or allow him to reside in the house for a period equivalent to that difference.