My dad read the Hobbit aloud to me when I was 4 or 5. I probably read it myself by the time I was 10. I read LotR for the first time in college. I was in my late 20s when I read The Silmarillion.
I first read the Hobbit as a seven-year-old, but my family was poor and could not afford LOTR until I was eleven, and I read The Silmarillion a year later.