Hello, I'm Alicia. Thanks for your question, I'm happy to help you today. I'm sorry to hear about your stepfather's situation, and it does sound to me like he's dealing with some common issues that occur to a lot of people upon retirement -- maybe it's the lack of a feeling of purpose or some other underlying issues that have led him to start living a life of (what sounds like) lethargy. Obviously, I can't say for sure what's going on with him without meeting him, so I do think it's important that someone suggests professional intervention to him before things get worse. It does sound like may be suffering from depression (although again, I can't really say for sure just based on our conversation here) and that it's possible that this situation may spiral downward if he doesn't get some professional help. Unfortunately, because he is an adult and it doesn't sound like he's a danger to anyone but himself at this point, no one can force him to get help, it's something he needs to voluntarily agree to. I would suggest (if you are close to him) that you sit down with him and let him know how concerned you are for him and his health and well-being. Try to come from a positive viewpoint, in terms of focusing on your concern and love for him and not on blaming him for drinking or laying around, because that might only cause him to become defensive. I realize that a large part of this is either caused or exacerbated by his drinking, but I do feel that if you try to address that issue with him directly (and you already say he's stubborn) he might just shut you out, so just to reiterate, try to focus on your concern for his health and overall well-being. It's not your job to be his therapist, but you can help him seek the right type of help if he is open to the idea. If you don't feel comfortable talking to him about it, then it's up to your mother to do so, although since you say she's feeling irritated with him, I can imagine that it might be hard for her to have this discussion. You might even consider talking to him together -- I would talk it over with your mother and see what you both feel comfortable with. Also, be patient -- it might take a number of attempts before he actually decides to seek help -- but just remember that the decision is ultimately up to him. If you need help finding a qualified therapist in the area (it might be good if you help him by saying that you've done some research and have found a few therapists nearby -- IF he says he is open to it), you can search on this website (obviously, it depends on where he's located, you can narrow the search options by city): https://therapists.psychologytoday.com/rms/state/Michigan.html
Please let me know if you need additional assistance.