For all the effort our speaker puts into describing love, we wonder if it's really just another way of talking about death, which seems to lurk behind every line break in the poem. After all, while he describes the love that his brother and father had for him, he also contemplates their existence after death, whatever that existence may be.
Line 6: This question seems to contain an implied metaphor for death, in which the brother's demise is represented by the burning of the earth. In any case, the brother certainly can't come back from the dead, if his home has been torched. Ain't that a shame?
Lines 9: "What is dead is restless," describes the dead, sure. But can we trust what the speaker is saying here? It might be the speaker projecting his emotions onto his imagined brother, or even a kind of personification of the "what" that is dead.
Line 26: We've got some seriously crazy imagery here, describing God's turning things and humans to ash. But these descriptions of God also serve as a symbol of the way that everything that dies turns to ash (or dust) in the end. God is the agent of that death, that transformation to ash, because he's a furnace, with gasoline breath.