When the Obamas move into the White House, they will bring their two daughters, Malia and Sasha. The Bushes also had two daughters, Jenna and Barbara. And of course, the Clintons had Chelsea. Lots of Presidential daughters in the last three administrations.
This got me thinking: when was the last time there was a boy - i.e., a son younger than 18 - in the White House? Turns out that it's been a while. The last male descendant of a president to live in the White House while younger than 18 was John F. Kennedy, Jr., 45 years ago. The Kennedy's had another son after John John, Patrick, who died two days after he was born.
Lyndon Johnson and Richard Nixon both had two daughters. Gerald Ford had four kids. His youngest son, Steven, turned 18 just two and a half months before his father assumed the presidency. Jimmy Carter had three sons and one daughter; the three sons were all adults when Carter was elected. Amy grew up in the White House.
So it's been a long time since there's been a little boy running around the White House. Not important, really, but sort of interesting.