CHARLES CITY, Va. (CBS) -- John Tyler was the first vice president elevated to the presidency on the death of the chief executive and the first president to marry in the White House. Nearly 175 years later, two of his grandchildren are still around.

Harrison Ruffin Tyler, 89, is one of two living grandsons of President John Tyler, who was born in 1790, one year after George Washington was sworn in as president.

Just three generations -- President Tyler, his son Lyon Tyler, and grandson Harrison -- span almost the entire history of the United States.

William and Harrison Tyler CBS NEWS

We met Harrison and his son William at President Tyler's Virginia estate. We asked William if people find it hard to believe that his father is the grandson of the 10th president.

"I find it hard to believe," he laughed. "I think it had to do with second wives."

Here's how it happened. John Tyler became president in 1841. He had eight children with his first wife, who died while he was in office. At 52, he married 22-year-old Julia Gardiner. They had seven children, for a total of 15 -- the most of any president. He was 63 when son Lyon Tyler was born, whose first wife also died. Lyon also had a very young second wife, and was 75 years old when Harrison Tyler was born in 1928.

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