"You will be free as soon as you are twenty-one, but I am a slave for life! Have not I as good a right to be free as you have?" These words used to trouble them; they would express for me the liveliest sympathy, and console me with the hope that something would occur by which I might be free.
This means that in the text the men would be free as soon as they turned twenty-one, but the one person would rather be a slave for life, he was wondering if he will be ever free like the others and he needed to the hope that he will be free like the others from being a slave.