As for Blaze's age, it is not explicitly stated in the show. However, according to an interview with the show's creator, Jeff gowler and according to the blaze wiki Blaze is 6 years old.
The show’s creators intentionally keep Blaze’s age vague to let young viewers see him as an aspirational, older "big brother" figure. However, several episodes provide enough evidence to narrow it down: how old is blaze from blaze and the monster machines