Both a good friend of mine and me had to deal with this inside a year with our dads. Mine was a bit more of a suprise to the family as dad had a condition that wasn't diagnosed until about a week before he passed. His dad was a bit more of a known quantity as he had been ill for years.

My dad was in a coma for about 5 days before he passed. My friend's dad was lucid and somewhat functional, but his kidneys had failed and he was in Washington State, so he was visiting "for the last time" as the doctors had given him about a month (ended up being 2 weeks).

We talk about our dads quite a bit and this comes up very often between us. You are not telling them that it's OK for them to die to end your suffering. You are telling them that you love them, that you understand that it is time for them to leave you, and that they need not suffer on your account.

I think it was easier with my dad as I didn't have to see him respond to me telling him it was OK to go. I'm convinced he knew what was going on as we were having some very intense conversations regarding family, and when discussing a particularly difficult family subject about an uncle who he loved dearly, he started trembling and groaning. My cousin went to his bed and whispered to him that we would not talk about it any more and he stopped being aggitated, despite having slipped into a coma at this point. I know he heard us and convinced me that a coma is not necessisarily a complete lack of awareness. Therefore I know he knew I was OK with him no longer needing to fight a battle that we knew the outcome to. He passed the next day after I and my brothers talked to him about it.

My friend was a lot different, but they were able to have the discussion "you have fought this enough, I will grieve when you are gone, but it's OK to go." His dad passed a week after he left to come back to Virginia.

You are giving them the reassurance that you are ready to handle the burden of their passing and that they leave this life with your love.