Directors of a company must fulfil a minimum set of statutory duties. The link below will produce one version of such a list of duties - this one from the Institute of Directors. There are others that are similar.
http://www.iod.com/intershoproot/eCS/Store/en/ pdfs/dutiesresponsibilities.pdf
In certain circumstances a director may be personally liable for certain failings of the company
It is a potentially valid defence that a director may claim that he/she had reasonable grounds to believe that a competent person was looking after the statutory duties - in this case the brother who seems to be an executive office of the company as well as a director.
The example you cite is strange; what I think you may mean is that the company is in breach of a statutory duty to do with the environment, that may result in a fine for the breach, the company can't pay and so has collapsed.
In particular, sections of the Health & Safety at Work Act 1974 are covered by a duty on directors, but there are others. What happened? - pollution into a river, perhaps?