luluspice
I've had a look at the legislation and as far as I can see the maximum period by which a UC claim can be backdated is one month, there appear to be no circumstances where this can be extended.
It may be possible to claim compensation from the DWP if you can show that he was incorrectly advised when he first tried to claim UC but if the mother was his DWP appointee then I think you will struggle to show an error.
Gordon
Nothing on this board constitutes legal advice - always consult a professional about specific problems