I am not convinced he could rent his half either, but if they were tenants in common, then this could be why the judge has come to the strange conclusion that he has (Based purely on the fact that as a tenant in common in which case, the mother would not automatically inherit the other 50% of the property if the brother died which she would do if they were joint tenants)
Either way I think this is a family arrangement as would the brother rent out to someone off the street in order for them to reside in the property looking after his mother. Not likely as he would have to pay them to do so.
