DS1500 form BLUE BADGE

My stepdad is terminally Ill with prostate & 2ndry bone cancer, he now struggles to get around even with a stick for any sort if distance. Would it be worth me perusing trying to get him a blue badge? I see he will need a DS1500 form is this done by his doctor? It doesn't seem overly clear online! If anyone could offer me some advise or point me in the right direction it would be greatly appreciated :)