“He understood what was going on, he was upset,” said his son William Tyler, 58. But “he doesn’t have any memory of yesterday, he doesn’t have any memory of today.”

Due to a series of mini-strokes starting in 2012, Harrison lives almost without time. It would be quite a change for anyone, but it’s particularly so for someone like him, who grew up steeped in family history. Harrison was raised in his grandfather’s hunting lodge; his grandfather — John Tyler, the 10th president of the United States — was born in 1790.

That is not a typo — 1790, as in, during George Washington’s first term.

John Tyler, an enslaver who was thrown out of his own political party, the Whigs, for vetoing so many bills, never makes it onto lists of best presidents. But he certainly made his share of history in the White House, where he served from 1841 to 1845. He was the first vice president to assume the presidency upon the death of a president; the first president to have a veto overridden; the first president to endure a House impeachment vote (it failed); the first president to be widowed and to marry while in office; and the president who fathered the most children — 15!

Because his second wife, Julia Gardiner, was so much younger, Tyler was still fathering children throughout his sixties. One of those children was Lyon Gardiner Tyler Sr., born in 1853, nearly a decade after his father’s term in office. Lyon Sr. ended up following a similar domestic path, being widowed and then remarrying to a much younger woman. They had Harrison when he was 75 and she was 39.

Harrison is also related to William Henry Harrison, the president his grandfather replaced, hence his first name. And he’s related to Pocahontas — “like 10,000 other people,” William said — but because of his unique bridge to the nation’s past, “there’s a high likelihood that he’s the closest living genetic relation to Pocahontas in the world.”