If my stepfather dies, who will be able to claim on his estate? My mother is already dead. I believe my stepfather has a son.
I take it your mother didn’t leave a will. In that case, unless she left property and assets worth more than £250,000 in her own right, everything will have gone to your stepfather. Unless she was supporting you financially at the time of her death you will have no claim on her estate, and it now belongs to your stepfather to dispose of as he pleases. If he doesn’t leave a will it’s likely that everything he owns will go to his son: it certainly won’t go to you. Your mother should probably have made arrangements in a will for you to receive her share of the house when your stepfather dies.