Douglass uses the phrase "his brother's blood." The pronoun "his" refers to Mr. Gore.
Who is the "brother"?
Text: His horrid crime was not even submitted to judicial investigation. It was committed in the presence of slaves, and they of course could neither institute a suit, nor testify against him; and thus the guilty perpetrator of one of the bloodiest and most foul murders goes unwhipped of justice, and uncensured by the community in which he lives. Mr. Gore lived in St. Michael's, Talbot county, Maryland, when I left there; and if he is still alive, he very probably lives there now; and if so, he is now, as he was then, as highly esteemed and as much respected as though his guilty soul had not been stained with his brother's blood.