The news of the recent death of Lyon Gardiner Tyler, Jr., aged 95, grandson of 10th U.S. President John Tyler (1790-1862), leaves just his younger brother, Harrison Ruffin Tyler, aged 91, as the last grandchild of a president who was born during the administration of George Washington, and whose term in office began twenty years before the Civil War. I’ve always been fascinated when hearing that John Tyler had two living grandsons and would occasionally confirm their longevity. The reason President Tyler has such extended generations is due to a second marriage at fifty-four years old, in the last year of his presidency, which resulted in seven children born between 1846 and 1860, the youngest when Tyler was seventy years old. Tyler’s youngest child, Mrs. Pearl Tyler Ellis (1860-1947), died over one hundred years after her father served as president. Lyon Gardiner Tyler, Sr. (1853-1935), fifth of the seven children from the president’s second marriage and the father of these Tyler grandsons, also had a second marriage at the age 70, resulting in these two grandsons (and a younger brother who lived only ten days), born between 1925 and 1931, the last when Lyon Gardiner Tyler, Sr. was seventy-seven years old.
Part of the reason these extended presidential generations are rare is that most presidents have had their children before serving as commander-in-chief, many already having grandchildren. Only three presidents have had children after leaving office (Tyler, Grover Cleveland, and Benjamin Harrison). After the only surviving grandchild of John Tyler (who served 1841-45), the next president (in order of administration) with a living grandchild is 22nd (and 24th) President Grover Cleveland, who served 1885-89 and 1893-97. Cleveland’s youngest living grandchild is Margaret Folsom Cleveland, born in 1956, through the second marriage of the president’s second youngest child, Richard Folsom Cleveland (1897-1974).
…Eliza Newell Garfield (who has one adopted daughter) is the only person who descends from three presidents…
Twenty-third President Benjamin Harrison, who served 1889-93 (between Cleveland’s two terms), and the only other president besides Tyler and Cleveland to have children after leaving the White House, also had (until very recently), one living grandchild, Dr. Jane Harrison (Walker) Garfield (1929-2020), who died 22 September 2020 (only four days before Lyon Gardiner Tyler, Jr.). Jane married Newell Garfield (1923-2003), a great-grandson of 20th President James Abram Garfield. Their daughter Eliza Newell Garfield (who has one adopted daughter) is the only person who descends from three presidents (Garfield and the two Harrisons).
On the other side of the coin, in terms of “condensed generations,” only nine presidents have lived to see great-grandchildren (John and John Quincy Adams, Jefferson, Monroe, William Henry Harrison, Hoover, Ford, Carter, and G.H.W. Bush). No presidents have lived to see great-great-grandchildren (Jefferson was only shy by seven years). President Jimmy Carter, aged 96, was credited with 22 grandchildren and great-grandchildren earlier this year, although the president’s eldest great-grandchild is only fourteen!
Source: For a detailed summary of presidential descendants, see Charles Mosley, American Presidential Families (New York, 1993).
 There are several double presidential descendants via the two Adamses, the Harrisons (without Garfield), the Bushes, and descendants of Eisenhower and Nixon.