You misunderstand the doctrine of the overlapping generation.
King George V was born in 1865 and died in 1936.
Queen Elizabeth II was born in 1926 and overlapped King George V by 10 years.
Prince Charles was born in 1948 and has overlapped Queen Elizabeth by 67 years.
Prince William was born in 1982 and has overlapped both Queen Elizabeth and Prince Charles by 33 years.
Prince George of Cambridge (becomes King George VI upon his coronation) was born in 2013 and has overlapped Queen Elizabeth, Prince Charles, and Prince William by 2 years and 9 months.
For both King George V and Prince George (future King George VI) to be of the same generation they must both have overlapped the life of at least one person in common. This is Queen Elizabeth.
Therefore they are all one generation. 1865 to Present. One generation.
Now if Prince George, on becoming King George VI can live at least as long as his great-grandmother, Queen Elizabeth, the overlapping generation could extend from 1865 to 2103.
It's simple overlapping math: 1+1+1+1+1 = 1
Of course by 2103 Prince George (as King George VI) might have children, grandchildren and great-grandchildren. However these four generations are only part of the one true overlapping generation of the "last days of this system of things" that started overlapping in 1865 with the birth of King George V.
