Think any notable US presidential children/grandchildren could be a shout, a lot of newspapers/news sites often obit them (although they're mostly low hanging fruit due to their age).
Harrison Ruffin Tyler (John Tyler's grandson, turning 96 next year, was mentioned several times across the forums and when it was discovered he's still alive the news got pretty big media coverage; additionally, he's been suffering from dementia for the last 11 years and had multiple mini-strokes)
Eleanor Roosevelt Seagraves (FDR's granddaughter, turning 97 in March, she and her brother Curtis-who died in 2016-were pretty popular in 1930s as "Buzzie and Sistie", she often attends Democratic events; she gave an interview in May this year and still looks sharp, but at her age it can change at any given moment)
John Roosevelt Boettiger (another FDR's grandchild, half-brother to Eleanor, turns 85 next year, widower and retired psychology professor; pretty much a stretch, but one for the future? Maybe, maybe not, more likely not, but still.)
Franklin D. Roosevelt III (same deal as John, turns 86 next year, retired economist and academic close to Hillary Clinton, haven't seen many news about him recently so I really can't judge)
Luci Baines Johnson (Lyndon B. Johnson's daughter, turns 77 next year, philantropist; seemingly in good health at the moment but she suffered from pretty rare Guillain–Barré syndrome back in 2010) and her sister Lynda Bird Johnson Robb (who turns 80 next year and is currently the oldest living presidential child)
Susan Ford Bales (Gerald Ford's daughter, the youngest person on this list-turns 67 next year-but suffers from heart problems and has been living with a pacemaker for the last 13 years, so possibly a name for a distant future?)
I know most names on the list seem like a long stretch, but I also think that some of them on it could be considered for the DL, in the future at least that is.