My brother is 48 and lives with my mother (78). Dad died 16 years ago. They are stuck in an awful enmeshed/co-dependent/dysfunctional relationship.
Basically, brother had very bad anxiety and depression in his late teens and early 20s. He did A-levels and went away to university but dropped out within weeks and came home. I don't think he could cope with the social side. He then completed the degree at a local university and lived at home. After graduation, his mental health deteriorated and he withdrew to his room. My dad would get angry and have goes at him and demand he got a job, but in the end gave up. For years he just lived at home with job and no relationships doing nothing.
When he was 31 dad died. After that he came out of himself a bit and began internet dating, returned to same local uni and did an MA (literature). I had married and moved out by then.
He's never had a proper job (a couple of very short-term delivery jobs that lasted a month, and a year or two writing articles for a content site). He has basically got a blank CV. I think he also feels a lot of shame at his life. He's ashamed to be 48 and living with his mum, ashamed to have never left home, ashamed to have never had a proper/long-term relationship, etc. He's also paid no National Insurance or income tax, and so, presumably, will get no state pension (is that correct??). People think he's a lazy parasite living off my mother, but to be fair to him she likes him being there. After dad died, I don't think he felt he could leave. He's very comfortable, and is happy for her to fund his life, but she's equally happy to have his company and support. They live in a fairly isolated spot, and my mother would never cope there on her own (she's crippled with anxiety and has been on Prozac ever since dad died).
Obviously, I worry about the long-term. If mum gets ill and has to go into a care home, the house wold have to be sold to pay the fees and he'd literally be homeless. Even if that doesn't happen, and mum dies suddenly, once the house has been sold and everything has been divided between the two of us, he'll have just enough to buy a one-bedroom flat. But let's say he's 58 when that happens, how will he pay for heating, food, council tax, electricity, and so on? And what's he going to do without a state pension? I can't raise this with my mother because she just goes into meltdown (shaking, crying, etc). And my brother is so withdrawn and twisted up with shame that he refuses to talk about it.