What is the ruling on taking a small amount of money from one's brother, knowing that it is ill-gotten, and am I sinful if I am not in need of it?

If your brother's wealth is a mixture of lawful and unlawful, there is no harm in benefiting from what he gives you, though this dislike increases with the increase of the unlawful. However, if all his wealth is unlawful, then it is not permissible for you to accept anything from him. You must advise him to abandon unlawful earnings and explain the consequences of his actions, and not accept his gifts if all his wealth is unlawful.