Answer:
Metaphor.
Step-by-step explanation:
Carl Sandburg's poem "Kin" uses the metaphoric literary device to lay emphasis on the "fire" image.
Metaphors are a form of literary device that writers use to compare words or phrases to an object or any action by the characters. But these comparisons are not applicable in the real world. Likewise, Carl Sandburg's use of "the fire" in the poem to compare the speaker with a "fire' is not applicable in reality. But with the use of metaphor, he can use the image of "fire' to perfectly show the nature of the speaker. He will not be a literal fire but his nature will be like that of a fire.