Yes he can. But to do so, he will need a litigation friend. This person must agree to conduct the proceedings on his behalf, agree to bear any adverse costs, and not have an interest adverse to your son's. Litigation over probate can be extremely complicated and is very often heard in the High Court Chancery Division (unless it is under the county court limit of �30k or all the parties agree) so I would suggest that you seek legal advice. As it is your son claiming, he may be able to obtain public funding (I say may as this is not always the case).