Give advice if they are open to it. Let them know some reliable sources to research. Don't push too hard. If they are not open to your advice then just accept it and let them live with their decisions.
And never offer more than a suggestion, or just tell what you would do in a similar situation. If things go wrong, you certainly don't want them coming back and placing the blame on you.
I mind my own business unless my friends or relatives ask my opinion. If they do, I remember that they’re adults who can make their own choices, including whether or not to follow my advice.
Be free with advice, but don't take responsibility for their decisions.
I have someone in my life that would make me responsible for every decision, and responsible for every bad outcome, and that's difficult to deal with. So I give them general advice but I don't specifically tell them what to do or not to do... To do anything else would invite them to constantly complain when they're investment loses money. For the rest of my life. I don't have time for that
i have watched my dad get completely scammed by the process of entering a retirement community over the past three years. nothing illegal, but taking every penny from retired folks is big business! our family is notoriously stubborn and nothing i said or did seemed to make a difference.
Try to ensure, if they won't listen to you, that they at least have a lawyer present when signing away their life savings. and several years before that even happens work with an advisor (who is actually looking out for customers' interests...shop around fire the advisors until you find one who isn't a con-man) to shelter as much money as possible. i failed at getting him to do either of those things.
There's only so much you can do. You can't directly control them. You ask tell them to stop. You can try to explain what they are doing is bad or dumb, but yiu can't stop them.