Lyric discussion by rhiannoncabalist 

Cover art for The Sons of Cain lyrics by Ted Leo and the Pharmacists

WHOOOPS the rest of my theory got cut off before I posted it.

OR could you take it that a spouse died, was murdered, but the singer doesn't know by whom and is looking at everyone else (all humanity) as the Sons of Cain... murderers.

"Have you gone on to their heavenly fame"

and that line is what really makes me think it's about the death of the singers' spouse.