Possible grandchildren on person born in 1776?

In My Humble Opinion
1

I was reading the other day that a grandchild of President John Tyler, born in 1794, was still alive. I looked it up and it was true.
the wiki article is two years old:

According to the Wikipedia article on John Tyler (1790–1862), Tyler had, by his second wife, Julia Gardiner Tyler (born 1820), a son, Lyon Gardiner Tyler (1853-1935). It says that Harrison Ruffin Tyler, a son of Lyon, was born in 1928 (when Lyon was 75) and is still alive.

So, John Tyler at age 63 had a son Lyon Gardiner Tyler, and Lyon Gardiner Tyler at age 75 had a son Harrison Ruffin Tyler, and Harrison is about 80 and still alive. 63 plus 75 plus 80 equals 208 years. Three generations span the years from 1790 and 2009. Amazing.
So, I am wondering if there are any grandchildren still alive of someone born in 1776? That would be 226 yrs ago. 70 yrs old + 70 + 86 (grandchild) = 226.
Looks like it is feasible. It would take two consecutive generations having children very late in life (old man, young woman) plus a long living grandchild.

2

Interesting, because in the 1991 edition of the Guinness Book of Records there was a category for this.

GENETIC AND QUANTITATIVE ASPECTS OF GENEALOGY states:

An extreme example of long generation intervals was quoted in the Guinness Book of Records (1991 edition). Baroness Elliot of Harwood was an active member of the House of Lords until her death in 1992 at the age of 89. Her grandfather was born in 1786, her father in 1823 and she was born in 1903. Thus, the generation intervals were 37 and 80 years respectively, with a mean of 58.5 years, and the interval between her grandfather’s birth and her death was 206 years. It is quite likely that this record has been exceeded in the past when both a father and a son, with younger wives, had children in old age.

So not as good as your find. They don’t have the record on their website but perhaps you could interest them in it.