he can get a certified copy of his birth certificate like JohnL said
Technically, that is very right!
Every UK birth certificate, marriage certificate etc says on it that it is a certified copy of the entry in the Register. The actual record is kept in the Register Office where the birth etc was registered.
So if we are talking about a birth certificate issued when the birth was registered, that will say it is a certified copy ..... and if another copy is issued now, many years later, that will also say it is a certified copy.
But the important point is this. The newly-issued copy is
not a certified copy of birth certificate handed to the parents many years earlier. Both that issued-soon-after-birth one and the newly-issued one, are both copies of the entries in the Register at the Register Office ... and both are just as valid as each other.