Wouldn't be the first time POTUS posted here, or the first time Q/Q+ posted anonymously; the JFK = Lark thing is interesting, and fits in with the rest of the family nicknames, but doesn't really click with "when does a bird sing".
THE PRESIDENT AND HIS FAMILY
LANCER President John F. Kennedy
LACE Jackie Kennedy (First Lady)
LYRIC Caroline Kennedy
LARK John F. Kennedy Jr.
THE VICE PRESIDENT AND HIS FAMILY
VOLUNTEER Vice President Lyndon B. Johnson
VICTORIA Lady Bird Johnson
VELVET Lynda Bird Johnson
VENUS Lucy Baines Johnson