What would you advise?

Ugh, this 35yr old man sounds not only lazy and selfish but also downright unpleasant. Kick him out I say. Tell him to find his real parents if he thinks they can do so much better.

Good Luck to you and your BIL in persuading your SIL that the time has come to change the financial situation towards the "budding musician"

It sounds to that the sister needs her son as much as he wants their money. Does she need to have him around and be dependent on her to give her own life meaning.

I think the boy's mother's problems need to be addressed first and then kick him out.

Emotionally immature children of all ages will latch onto something to try and emotionally blackmail their children. Birth children will say things like 'I didn't ask to be born, you decided to have me' . His argument is just the adopted child's version. Both should be treated with the contempt they deserve.

When I had a difficult message of the kind described here I went to Relate to talk it through with an independant advisor. The problem was going round and round in my own head with no solution. Seeing Relate was a 'life saver' in that things were put into perspective and a suggestion made as to a path to follow.

I followed the path, resolved the situation to how I needed to, but of course the other person had to accept my solution. However I am still speaking to the other person concerned.

I agree with nokkie that any change needs to be gradual. Maybe start expecting the son to pay this bill or that or contribute X amount to household bills overall (pay a small rent). Let him figure out how to do it (i.e. work pt or ft, etc.). Increase it periodically (let son know this will happen).This will give both son and mom time to get used to the idea.

But first, bil needs to work this out with his wife. He needs to point to the realities of the situation, and let her know her refuses to go into savings, so compromise is necessary, Relate may help, as Fran suggests.

If they work out their differences, then, maybe they can present the situation to son together. Maybe let him help decide what bills he'll pay, etc. And, of course, he would also have the option to move out (I doubt he would). If he throws up the adoption, I would ignore it. It's emotional blackmail, as pps have said, and I wouldn't let it phase me. But that's just me, of course.

But I'm confused. Is bil your sister's dh or your dh's brother? Iows. is the mum your sister or your sil? If she's your sister, bil may really be asking you how to get through to her. But if he lets it out that he spoke to you, it could drive a wedge between you and her. Not good.

Even if she's your sil, however, I agree with those who say you're getting pulled into a husband/wife argument. Don't go there. The only advice I think you should give bil is to work this out with his wife. If he says he "can't" maybe mention Relate. That's it. The rest is up to him and his wife.

Apologies if someone has said this but what advice does your BIL expect from you? There is only one option open to him and I think the question he may be asking is how to assert himself? If he has always given in to his son, for peace say, he will find it very very difficult to suddenly become assertive.

I don't 'get' why his wife thinks they should carry on supporting him - IF they can't afford it, they can't afford it and even if they COULD afford it, they shouldn't be doing it! Where is this son's pride? Why does he feel he is 'entitled' to be treated like a dependent child? Does he have any other issues? Would it come as a huge shock if they just cut him off?

Just a simple from the heart sit down conversation

Son I am unwell now, actually not well enough to help as I have done in the past so sorry son I hope you understand

Hi Sunseeker. Is it too late to make a suggestion? Have you already resolved your dilemma?
I find all the answers given here very interesting. Everyone seems to make assumptions about the whole family, especially the musician/son. Would it be reading too much into other people's posts to think maybe there's an element of jealousy? Do people wish they'd had the opportunity to follow their own dream, and resent this unknown person for having so much financial help and support to follow his?
But to the point.
I think it's possible that your brother-in-law is casting around for another relative who might have the funds and the inclination to chip in now with some support.
But I think it's more likely that he's asking for support in what should really be a three-way family discussion. He probably feels bereft. I'm guessing everyone in that household is finding it difficult to come to terms with the new situation: father/husband (breadwinner) losing his health and no longer able to fund everything for everyone.
But these three people have been sharing a household (or at least an income) for many years, and so I think should face the new situation together. I would suggest your advice be that they have a "family meeting" and sit down to discuss the new situation and how best to deal with it. That way you can avoid giving either advice or opinion about their lifestyle to date (no one wants to know that people think they've been wrong in their choices!) You could possibly offer suggestions for them to discuss: eg maybe your brother-in-law could ask his doctor to put everything in writing so he can show it to his wife and son, so that they can understand his health issues; as well as all the ideas given in here eg claiming jobseekers allowance. You can offer practical suggestions for them to make decisions on, without even suggesting what you think of a 35-year-old who hasn't spotted that his father's ill and hasn't learned how finances work. And after all, it will be for the "young man" to decide if he would prefer to busk on the street or work "in macdonald's".
I hope you will manage to support your brother-in-law (if that's what you want to do) without alienating the whole family.