Given that he had no contact with his father and was therefore presumably not financially dependent on him, he has no claim regardless of the length of time elapsed. (I'm assuming England and Wales here - other countries may be different.
There is one possible gotcha in this - if the will left property to the father's children generically rather than to named individuals then I believe he would have had a case. Whether he still has I don't know - but papers from an estate have to be kept for 12 years so I guess there is a possibility he could claim the estate was maladministered.
Legal advice might be a good idea.