Is it permissible for me to benefit from the money of my brother who possesses 150,0 dirhams that are lawful and one million dirhams that are unlawful, which he stole from a wealthy Jew, knowing that my brother used to work for this Jew and the latter did not regularize his legal status as he had promised?

It is permissible to utilize a brother's lawful money with his permission, such as a benevolent loan or through Mudarabah (definition) (a partnership in which one party provides the capital and the other provides labor). However, it is not permissible to deal with unlawful money, by agreement of the jurists. What the brother did, stealing from the Jew, is forbidden. He must repent and return the money to him or to his heirs, unless the Jew had wronged him in his wages, in which case he may take the amount of his right and return the remainder. This is the issue of Al-Zafar (the taking of one's right from another who denies it).