"I think it had to do with second wives." Pretty much. CBS News is out with a good bit of historical trivia: John Tyler, who was born in 1790 when George Washington was president and became America's 10th president in 1841, has two living grandsons. As the network puts it, "just three generations ... span almost the entire history of the United States." The wild fact is indeed thanks to second wives.
Tyler's first wife died while he was president, and he married while in office, with the 52-year-old taking a 22-year-old bride. One of their seven children was Lyon Tyler, born when the then-former president was 63. Lyon also lost his first wife and then married a woman 35 years younger, per Snopes. When he was 75, in 1928, Harrison Tyler was born. He's now 89. CBS doesn't provide details on the other grandchild, but Snopes reports his name is Lyon Tyler Jr. (Speaking of America's earlier days, a copy of this important document was hidden behind wallpaper.)