I have a client who was claiming JSA until his GP signed him off sick and the jobcentre told him to claim ESA. On claiming ESA he failed the HRT. He and his family are of Spanish nationality and came together to the UK early 2008. He lives with his wife and children. Some of his children are grown up and work. Could he appeal the HRT decision on the basis that he lives with relatives who could be classed as "EU workers"? Or would it be better for his wife to try claiming JSA?

As he has (presumably) never worked in the UK he can't satisfy the contribution conditions for CBESA and is not a worker himself.
To claim as a family member he is going to have to show dependency ("dependent direct relatives in the ascending line"), and at the moment the jury is still out on Jia and whether you need to show dependency in the country of origin or only as at the date of claim.
Was he living with the children who came her to work, and did he come at the same time? Do they provide him with free accommodation?
Is there any reason why the wife can't claim JSA - is she reasonably likely to find work?