No! Carolyn Keen is a pseudonym for many writers.
Yes, Marco and Justin Keene.
Carolyn who?
Carolyn Keene is actually a pseudonym used by several authors for the Nancy Drew mystery series, so there is no specific individual named Carolyn Keene who has died. The original founder of the pseudonym, Edward Stratemeyer, passed away in 1930.
Carolyn Rodgers died in 2010.
Carolyn Hougan died in 2007.
Carolyn Merrick died in 1908.
Carolyn Harris died in 1994.
Carolyn Sherif died in 1982.
Carolyn Haywood died in 1990.
Carolyn Hurless died in 1987.
Carolyn Cudone died in 2009.