A younger man has befriended my grandmother. I worry he’s a threat

I fear my 85-year-old grandmother is at risk. She was diagnosed with Alzheimer’s disease two years ago and lives alone in sheltered housing. She refuses to accept the diagnosis or any related assistance.

Over the past year, a man in his late 50s has befriended her. Their relationship has grown; he has been visiting her often and, in our eyes, become controlling. My grandmother trusts him entirely. Her relationship with her four children (my father and his siblings) has been strained at times over the years. However, the arrival of her new “friend” has coincided with her refusing to trust their judgment. This has caused a much greater rift, and we are worried that this man is easily able to manipulate someone in her position.

My aunt arranged for social workers to visit her, and they were satisfied she was not at risk. We cannot get help from the police because the man has not committed a crime, nor can we take legal action. My aunt and uncle have power of attorney, so this person cannot gain control of her assets; what else can we do?

You didn’t mention exactly what you are worried your grandmother is at risk of, but I’m presuming abuse of some kind – physical, emotional or financial – and I understand your concern. Are there any signs of abuse? Much as we’d like this man’s friendship to be benign, the fact that you think it isn’t should be taken seriously. Her refusal to accept her diagnosis, any assistance, and her trusting her new friend over family is a familiar problem.

I consulted three different specialists: lawyer Gary Rycroft, who specialises in advising elderly clients; charity Age UK; and Rachael Clawson, a former social worker and now associate professor in social work at Nottingham University, and lead of a study on forced marriage.

While it’s good news that your aunt and uncle have lasting power of attorney (LPA), that doesn’t mean that this man couldn’t eventually gain control of her assets. It sounds as if your grandmother is widowed. If so, then she is at risk of predatory marriage. This wouldn’t overturn the existing LPAs, but it would mean that, on your grandmother’s death, he would inherit the first £270,000 and half of the rest of the estate. (A marriage revokes any pre-existing will.)

Furthermore, it’s not just about money; he would have control over her funeral and her belongings. I’m sorry to talk about such a sensitive subject, but it’s better to be forewarned.

A vulnerable person could be coerced into marriage: the checks for “capacity” for marriage are less rigorous than they are for, say, altering a will. Rachel Clawson is campaigning for change, proposing that registrars should be more carefully trained in spotting someone who may not have the capacity to agree to marriage, and also that notices of forthcoming weddings should be published online.

Both Rycroft and Clawson recommended that if you have concerns, you should contact your local register office, and those in surrounding areas, to put a caveat in place to give notification for marriage. That way, the registrar has a note that there are concerns, and, if necessary, social services could be called in.

Related: I’m terrified that I will die, leaving my son. How can I cope?

Rycroft also recommended keeping close to your grandmother and her friend. “Like handling teenagers, do not make someone you disapprove of even more special by your disapproval. Keep an eye on the situation; do not let any potential abuser drive a wedge.” Can you step up your visits to her? Your grandmother may be lonely and flattered by the attention. She may even, on some level, know (if this is the case) that this man’s attentions are not in her best interest. Sadly, this is not uncommon, but she may be so desperate for company that she goes along with it.

Although it’s not a replacement for in-person visits, I recently bought a Komp for an elderly family member. It is brilliant: you can video-call, or send photos or texts, and the one-button unit is super simple for someone unfamiliar with modern tech.

If there is a warden in her sheltered housing, could you alert them? You can also keep on at social services, but, ultimately, unless she is living full-time in a care home or with family, you can’t keep watch 24/7. Age UK, We Are Hourglass and the government’s Forced Marriage Unit have good resources you may find useful .

Every week Annalisa Barbieri addresses a family-related problem sent in by a reader. If you would like advice from Annalisa on a family matter, please send your problem to ask.annalisa@theguardian.com. Annalisa regrets she cannot enter into personal correspondence. Submissions are subject to our terms and conditions: see gu.com/letters-terms.

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