It is reasonable that John the Baptizer, who was a Levite and son of a priest, began his ministry at the same age, not at the temple, of course, but in the special assignment Jehovah had outlined for him. (Lu 1:1-17, 67, 76-79)
... The specific mention (twice) of the age difference between John and Jesus and the correlation between the appearances and messages of Jehovah’s angel in announcing the births of the two sons (Lu 1) give ample basis for believing that their ministries followed a similar timetable, that is, the start of John’s ministry (as the forerunner of Jesus) being followed about six months later by the commencement of Jesus’ ministry.