Is it permissible to eat from the money of my brother who works as a composer of songs, knowing that he has no other source of income, and my father is deceased, and I am unable to earn a living?

It is permissible to eat from his money out of necessity, because he is obligated to spend on you, and you may take according to your needs. You must advise him to abandon the forbidden work and seek another job, and clarify the ruling of Islamic law regarding singing and music, and the impermissibility of cooperating in sin.