Read the lines from Langston Hughes's poem "I, Too, Sing America."

I am the darker brother.
They send me to eat in the kitchen
When company comes,
But I laugh,
And eat well,
And grow strong.

Why does the speaker use the word "brother" in the first line of the stanza?

to indicate that he is someone’s brother
to indicate that his family makes him eat in the kitchen
to indicate that the arriving company is family
to indicate that people belong to same metaphorical family