AynaDee, so sorry to hear that your cousin was in so much pain that he felt leaving would be better...
i HAVE been in that place...it's not that you don't know you'll cause loved ones pain...it's that you feel they'd be better off with you gone. I know it's irrational, but when you are in such despair, and feel that there is no way out (another irrational thought, I know), then death seems like the only choice.

I hope that you understand that he was trying to end the horrible suffering he was experiencing...