Hi, thanks for your answers. The person in question is retired and moved to the UK about 2 years ago together with his wife (whom he lost soon afterwards). They moved as "older relatives who needed care" or something like that. Their daughter is married to a UK national, I'm not sure if she has the UK citizenship or just the residency. He mentioned that the original petition was rejected (I'm not sure why), then with the help of a lawyer the situation was sorted out.
Since his wife's death he feels kinda lonely and trapped and was thinking maybe he could remarry. Financial requirements shouldn't be a problem, he's got funds & a decent pension.
His daughter thinks he's nuts and is unwilling to help, so I told him I'd ask around, asking is free of charge.

Now I'm curious myself how all this stuff works, I've always been very good with paperwork.
Yes, he probably could get in touch with a lawyer, but he says he's not ready for drastic steps yet.