If the kids are suffering, they need to be removed from the situation, no ifs or buts. All you can do is keep being there, maybe speak to drug addict associations for advice. Definitely keep a close eye on your dil and grandkids, make sure they’re safe and well

Dear troubled mom,
this is a very difficult situation you are in; I have been there with a dear friend who is a heavy alcoholic, porn, cigarettes and women addict. He is just a friend but the impacts on his environment is devastating: lies, promises, hurts, dementia… like you said: one cannot help unless they ask for help, we can be there and try to comfort the family but we are humans. These diseases begin in the soul, in the Spirit of the person. Who else could know the cure than the CREATOR!! You need supernatural help first for yourself to be healed, made whole, strengthened with power outside of yourself and with patience, goodness, peace, gentleness, meekness. At this season of Christmas I ask you, has the reality of a baby sent by our Creator to save the world, to save you hit home? Then I ask you you have nothing to lose but EVERYTHING to win, get yourself a Bible (Hebrew Scritpures plus New testament) start reading and open your heart to the love of the Saviour. Only HE can help you in your situation and heal your son. May you find your Saviour who died on the cross 2000 years ago yet waiting for you to allow Him into your life, into your circumstances; there still is power in HIS resurrection for you to reach out and receive everything your soul longs for: forgiveness, renewal, true life, divine love and supernatural power through the Holy Spirit to be a channel to help your loved one. It is a narrow road but it leads to true life. Shalom.

So hard ! You can’t really help indeed, unless he sees the problem and want help himself indeed. And unless there’s an acute danger, there is no reason for involuntary treatment.
What you can do is taking care for yourself: take distance when it gets too much for you. Encourage his wife and children to do the same. I know you probably don’t want to encourage a broken marriage, but the damage he’s causing now can be more damaging then a broken marriage and could cause him to get motivated to get help.

You need to look after your- self as well …if you go down you are little help for your son.
Drug and alcohol addiction are hard on the person and so very hard on the family and I wish you and your family all the very best and hope things improve soon.
Here are two web sites that may offer some information and help and I strongly advise a talk to your GP and services like Lifeline and the Salvation Army.
Much love and gentle hugs to you. xx
healthdirect.gov.au/how-to-help-someone-with-a-drug-problem
lifeline.org.au/get-help/topics/substance-abuse-and-addiction

You need to find support for yourself, and also treat him as though he does not have an addiction, take him nutritious meals, important as most addictions are made worse from lack of nutrients. There are many resources like AA for drug addicts to. My brother had a problem for years so I understand from my mother’s point of view what she went through and supported him when he needed it the most.