Hollywood undead song undead

my cousin is saying that he wrote undead by hollywood undead and I was wondering how I should test to see if he really did the fact that he did is really bugging me because there so famous which I found out today

well you could check the copyright on the lyrics, see who has the copyright. although im a big fan of hollywood undead, and im pretty sure they wrote it themselves, but if not there a 1 to a trillion chance that your cousin wrote it, just do some research on the song to see who wrote it