John Tyler's Grandsons
John Tyler was the 10th President of the United States and was born in 1790. There is a surprising piece of trivia that occasionally surfaces on the internet: John Tyler still has 2 grandchildren who are alive and well today (2017 at time of writing).
To help put some context on this, John Tyler was president about 20 years before Lincoln was shot and he was born under the rule of the first president, Washington. Consider that both Tyler, the 10th President and Trump, the 45th, both have grandchildren alive. It feels like he dates just shouldn't work out.
The reason this odd legacy was possible was because Tyler remarried a woman 30 years his junior after his first wife died. In total he had 15 children (8 with his first wife, then 7 with his second), with the last making its entrance into this world just after Tyler hit 70.
Of these children the 13th, Lyon Gardiner Tyler, had a similar life to his father. He too was widowed and remarried someone 35 years younger than him. In total he had 3 children with the second wife, although one died as an infant. The other two were born in the 1920s and are still just about alive: Lyon Gardiner Tyler, Jr and Harrison Ruffin Tyler.