Dowry hunter - Aunt's partner tries to cheat the grandmother

The boy can already butt in quite aggressively.
Imagined case: He goes to grandma and pesters her repeatedly to give him power of attorney over her financial assets, in case she can’t manage anymore. Because he doesn’t want to put this stress on his girlfriend (not wife!!!) and he’s the one who handles all the money matters for them anyway.
It would make sense for him to be included in the land register so that later, in case of inheritance, there is someone who can sell quickly and then distribute fairly to the heirs. Any one of us would tap our forehead. But grandma, who doesn’t want to be a burden on anyone and is not as sharp in her thinking anymore, falls for it and suddenly the matter is settled.

I just believe Kaho now, that the guy is a bit of a fool. Her aunt is indeed a dear person but very obedient to her boyfriend (not husband!!!). She can’t really take action but maybe she should listen closely to what direction the man is headed and sensitize grandma.

I notice with my grandma how easily manipulation works. Now she also has a processed brain hemorrhage. She can no longer organize many things properly in her mind.
My mother and my aunt (the wife of my grandma’s son by marriage) have full financial power of attorney. They brought it up at coffee and cake with grandma and suddenly they had it. Of course, we know they handle it responsibly and they could also check each other. But still, my aunt/my mother could now empty the account (which is not a small amount) and move to the Balearic Islands with it.
During our last visit, I casually mentioned what we still need to get for our offspring (actually to reassure my grandma that it was ridiculously little). Grandma immediately wanted to transfer me 5000€ so we could set up the nursery. I thanked her kindly and changed the subject. Fortunately, she forgot it quickly.
Cheating dear old grandmas is so very quick.

He goes to grandma and keeps pestering her to give him power of attorney over her financial assets, in case she is no longer able to manage them.

And how is Kaho supposed to prevent that? Do the same herself? I just see very limited possibilities to put what you find out into action.

My suggestion: Instead of arguing for 13 pages here, you should rather make an appointment with your grandma, your aunt, and any siblings you may have. Preferably without any additional people, and then you can discuss everything calmly. Please do not immediately bring up the inheritance, but rather how you can best support grandma as things are now and how it will be when she can no longer do as she wishes. Inevitably, you will also end up talking about the house during the conversation.

The boy can really intervene quite forcefully.
Hypothetical case: He goes to grandma and keeps pestering her to give him power of attorney over her financial assets, in case she can no longer manage herself. Because he doesn't want to burden his girlfriend (not wife!!!) with this stress, and he already handles all the money matters with them anyway.
It would make sense for him to be added to the land register so that later, in the event of inheritance, there is someone who can quickly sell and then distribute fairly to the heirs. Any one of us would hit their forehead. But grandma, who doesn't want to be a burden on anyone and is no longer as sharp in thinking, falls for it and suddenly the deal is done.

That corresponds to pretty much 100% of Mr. Habmichgern’s approach. It probably would have worked already if my grandpa hadn’t set different terms back then in wise foresight.

Tricking dear old grandmas goes so very fast.

That’s exactly it. And my grandma is very sweet.

My suggestion: Instead of arguing here for 13 pages, you should better make an appointment with your grandmother, your aunt, and any siblings you may have. Preferably without anyone else present, and then you can calmly discuss everything. Please don't start with the inheritance right away, but rather how you can best support Grandma as things are now and how it will be when she is no longer able to do what she wants. In the conversation, you will inevitably end up discussing the house issue as well.

Yes, we will first see how she is doing now. If things have actually worsened, then we will ask her if we should think of something together.

Didn't I read somewhere that she is not confused yet and can still manage her "business" herself? That she does not need a guardian? Letting things be is different from what you are doing. You are currently trying to interfere and manage... as I already said: for her, he is a family member who takes care of her - for whatever reason.