Is it permissible for us to eat the food brought to us by my brother from ill-gotten gains, given that it would spoil and we would throw it away, and that we are orphans with no income?

If all of a person's wealth is unlawful, it is forbidden to eat their food. If the majority or most of it is unlawful, it is disliked, unless the food was purchased with the exact unlawful money, in which case it is forbidden.

However, if you are poor and have no means of earning, there is no harm in you eating what he provides for you. Unlawful earnings, when their owner disposes of them and spends them on the poor and needy, become lawful for them. It is unlawful for its possessor, but lawful for the one who receives it by right.

If you are not poor or wish to abstain from it, then give it to someone in need. And it is obligatory upon you to advise your brother to avoid unlawful earnings.