Families decide every day to kill their brain injured relatives. No one, not even family, should be deciding to kill an innocent person.
I respectfully disagree. Sometimes, it is entirely appropriate that a family makes the hard choice.
Personally, I don't think it's fair for someone to ask their family to make that choice, so I have a living will with very clear instructions for such a possibility. That way the decision isn't theirs, but mine, and I hope if it comes to pass that makes a difference to them, relieving them of any feelings of guilt.
But if I hadn't a living will, I'd trust my wife to make the right choice for me.
Life is a gift from God.