I have both living and deceased close family members and friends who hoard/hoarded.
I don't believe they have any option but to live the way they do. Intervention, medication, therapy (if available) has not made a sustainable difference.
Each person who hoards is an individual, not all are unkempt and dirty, or live in squalor. I have a friend who hoards books, she would never recognise she is a hoarder, she is highly successful, high functioning, but the lengths she goes to store books is hoarding.
No matter how difficult it is do not judge, do not criticise and do not clean, move, dispose of any of their belongings without their absolute consent (and l would say active participation).
You will know, NanaT Tuesday, how softly you have to tread and probably emotional support is all you'll be able to offer. Moving a cup, removing a newspaper may cause the person who hoards to lose any trust they gave in you and communication will be lost.
All the people l know that hoard are very nice people, trying to cope with lives complicated by mental disorder. I always feel honoured (for want if a better word) that they trust me enough to be open about their condition. I see beyond the hoarding, l see the person.