Question: what is the age difference between kakashi and itachi?
Answer: In Naruto, Kakashi is 26–27 and Sasuke is 12. Sasuke was 7 when Itachi killed his clan so let's say 26–5=21 and Itachi became an Anbu the same year he killed his clan at age 13, so Kakashi was 21 when Itachi became an Anbu.