Yah, in this case, very headache ! 
I mean, when it comes to our own family members, the attachment is
definitely there. We just want to" fix the problem "no matter what.
In fact most probably we wld hope for a quick- fix if there's any.
And this is exactly where we might go to the wrong path.
There's no quick- fix soln in life. But it doesn't mean there's no
soln at all. Just that it takes time.
My method is to first tell the person the effects of his actions(
not neccessary mention the Dharma, although the theories may comes
fr Dharma, as he may reject it outright), n if he seems to agree
then I think the war is half won. The rest will be his own
decisions n choices, all we can do is to observe quiety n press the
emergency button again when he stray.
But in the case where he simply refuses to listen, then just let it
be for the moment. Not abandon, but to just step aside. Becos to
him, his actions is not a problem at all, we may be his problem!
So in this case, i wld just let him continues his lifestyle( of cos
provided no humans, animals, or properties r harmed 
), n just wait for the efects to manifest one day.
Then it may be possible for him to seek help n we can approach him
again. Yes, it may happens in days, mths, yrs, but it wld happen.
And yes, it may unfortunately happen when we r long gone, but it
will happen; n he will finally learn the lesson, albeit a little
too late perhaps. No matter what, we shouldn't be too hard on
ourselves in wanting to offer help. We help when we can, we stop
when we've reached our limits.; then step aside, come back later n
see wat happens. Things may hv changed, situations may hv change, n
there may be new soln.
This is wat IsIs mentioned, that sometimes we hv to wait for the
conditions to be ready for actons to be taken; or AndrewYap's
"theory of the thirsty horse".
