There was a 6 year old finisher in the 5th ever Honolulu Marathon back in 1977, Kevin Greenwell.
The SF Marathon in 2001 lists Kevin Greenwell as finisher #568 with a time of 3:53 and the correct age to be the same person.
I hope my marathon career lasts 24+ years.
Some interesting Stats from the Top 100 finishers for Hawaii 2003. Belgium - 1 Runner Ethiopia - 1 Runner Norway - 1 Runner Canada - 2 Runners, with the oldest runner (58) Germany - 2 Runners Kenya - 6 runners with 5 in the Top 7 USA - 22, with 17 from Hawaii Japan - 66 Runners! with the 2 youngest (17)
It appears the Japanese love this marathon, from 1990 to 2003 they have comprised about 60% of the entrants!