As the United States celebrates Presidents Day, an historical oddity continues: President John Tyler, who served from 1841 to 1845, was born in 1790, died in 1862, still has two surviving grandsons.

Lyon Gardiner Tyler Jr. was born in 1924. Harrison Ruffin Tyler was born in 1928. They are the sons of Lyon Gardiner Tyler Sr., one of President Tyler's 15 children.

"Both my grandfather — the president — and my father, were married twice. And they had children by their first wives. And their first wives died, and they married again and had more children. And my father was 75 when I was born, his father was 63 when he was born," Harrison Tyler explained to New York Magazine in 2012.

John Tyler became president in 1841 following the death of William Henry Harrison, who died on his 32nd day in office . Harrison holds the record for the shortest term in office as well as being the first president to die in office. His inaugural address lasted nearly two hours. He gave it in the cold, got pneumonia and died weeks later. Tyler became the first vice president to become president because of the incumbent's death

Author Gary May in a 2008 portrait dubbed Tyler an "Accidental President." He served until 1845. When he left office in 1845 Texas was on the cusp of entering the Union as a slave state. Tyler was a proponent of slavery's expansion; the nation's fierce division on the matter would culminate in the Civil War.

Both brothers' health have declined in recent years. But William Tyler, Harrison Tyler's son and John Tyler's great-grandson, spoke with U.S. News about the family's history.

" There was a book that was recently written and it voted John Tyler as the number one president," says William Tyler, president of the foundation for Sherwood Forest Plantation, President Tyler's estate. "Normally, he's one of the less recognized presidents."

William Tyler believes his great-grandfather upheld his convictions and the Constitution, and avoided disastrous foreign policy blunders as commander-in-chief -- "the things you really want a president to do," he says.

"So John Tyler actually scored really, really high in that unusual test. I thought that was kind of neat," says William Tyler.

Tyler's presidency is often ranked on the lower end by many historians , including a list published by C-SPAN on Friday . The book William Tyler referenced, "Recarving Rushmore: Ranking the Presidents on Peace, Prosperity and Liberty," came out in 2010 and ranked Tyler first.

William Tyler says while the family works to preserve the president's legacy, they have moved on and branched out, as well. His grandfather, Lyon Gardiner Tyler Sr., served as president of the College of William & Mary in Virginia, from 1889 to 1919. It is the alma mater of President Tyler, as well as two other presidents, Thomas Jefferson and James Monroe.

Harrison R. Tyler spent his career as a chemical engineer and businessman, eventually selling his company for more than $400 million, says William Tyler. The Richmond Times Dispatch reported that the company, ChemTreat , was sold for $435 million in 2007.

Tyler noted his dad's generosity.

"Over 100 of his employees made a million dollars," as a result of the financial structure of the company, William Tyler says.

Contemporary observers have sometimes compared the divisiveness of President Tyler's political era -- that culminated in the Civil War -- to the present day. William Tyler largely dismissed such notions.

"I think that every election that's going on, people feel that it's the most important, that there's never been one like it before," he says. "Just my opinion, that happens each and every time. And to me the good news is politics is a football that needs to be passed every now and then. If you don't, you're weighed down too much on one side."

Tyler adds: "The football just got passed."

"There were much more contentious times. Believe me, Andrew Jackson did not have a pleasant presidency," he says.

President Donald Trump has chosen a portrait of President Andrew Jackson to appear behind his desk in the Oval Office. Jackson served from 1829 to 1837.

A pugnacious populist, Trump's rise and politics have been compared the "Old Hickory," a popular nickname for the ex-general who first gained fame during the War of 1812 and the Battle of New Orleans. The Christian Science monitor wrote earlier this month: "Trump has embraced the idea that he's a modern-day Old Hickory, a populist outsider and scourge of Washington elites."

The plantation under William Tyler's care, Sherwood Forest, was named as such by the president after his time in the White House. Tyler, like Trump, was a member of many different political parties during his career. The name "Sherwood Forest" is a nod to the Robin Hood story ; Tyler was expelled from the Whig Party, then a major party, while president. Accordingly, he considered himself a political outlaw.

President Tyler was not unique in marrying a younger woman. The federal government is still paying a Civil War pension. A North Carolina woman, daughter of a veteran of that war, is still collecting benefits from the Department of Veterans' Affairs for his service.

Dan Pierce, a history professor at the University of North Carolina -- Asheville, who specializes in the American South, spoke to U.S. News about May-December marriages in generations of this era, and what might have contributed to young women sometimes marrying and having children with far older men.

"[There was] not much economic opportunity during this period," so many men would leave their native areas, Pierce said.