What is the ruling of Islamic law on taking a portion of the inheritance as compensation for a financial loss that occurred due to an act not intended as betrayal, and what is the ruling on my brother preventing and threatening me from receiving my inheritance from him until I compensate him?

What the brother did, forging checks, is considered theft, treachery, and fraud. He must repent and return all stolen money or seek the owner's forgiveness. The employer's satisfaction does not exempt him if the money he later displayed belonged to the employer.

What the sister did, helping her brother, is a kind human act. However, she is not permitted to dispose of her brother's money without his permission. Whoever borrows in a specific currency must return it in the same currency. The brother should not have held his sister accountable for her action. As for his desire to take a portion of her inheritance in exchange for his loss, if the borrowed amount was in the local currency, he does not have the right to take more than the borrowed amount, even if the currency's value decreased. However, if the loan was in dollars, the brother has the right to reclaim it in dollars, and he has the right to take what makes up the difference from his sister's inheritance if the relative did not return the full amount.