Select the most appropriate word to fill in the blank in the given sentence.

He is your brother, ______?

isn't he

The most appropriate word to fill in the blank in the given sentence is isn't he.

The sentence is a tag question, which is a question that is added to the end of a statement to ask for confirmation. In this case, the statement is "He is your brother." The tag question asks if the statement is true.

The answer isn't he is used to ask for confirmation of a statement that is about a male person. In this case, the statement is about a male person, so the tag question should also be about a male person.