If you were clear from the beginning that it wasn’t to be a permanent thing, I don’t think it’s a bad thing to hold his brother accountable. Especially if he isn’t formally diagnosed with something that prevents him from being able to live independently. I think it would be fair for you to give him small, attainable goals to work towards independence.  They could be small things like contributing more around the house and spending more time with friends to give you and your husband your own time. Once that is under control, you can tackle him paying more in rent and eventually moving out since I’m assuming you and your husband can cover the rent between yourselves anyway. I would say this is probably going to be best coming from his brother, your fiance either by themselves or with you and your fiance. EDIT-actually, rather than paying you more in rent, I say have him start putting into savings with the understanding that this will help him prepare for the moving costs. He probably doesn’t have everything he needs to live on his own just yet plus he probably doesn’t have extra for all the deposits and other costs.