Are there any other clues/evidence that support this theory? YES.
• MOST DISCIPLES WERE UNMARRIED
We only know of Peter being married (he had a mother-in-law), and men in that culture got married between the age of 18 and 20. We believe most of the disciples were unmarried when Jesus selected them.
• “LITTLE ONES”
Jesus refereed to the disciples as “little ones” a couple of times (Matthew 11:25, Luke 10:21, and John 13:33). Would be kind of strange if there were a bunch of old, bearded men.
There is some counter evidence for that as well. For example, John wrote the book of Revelation probably in 90 AD, and we assume he was around 90 years old when he wrote it. If Jesus was born in the year 4 or 5 BC (that’s the date most scholars believe), and if Jesus selected his 12 disciples at the age of 30 (that’s how old Jesus was, when he started his ministry), then that means it was about 25 AD when Jesus selected his disciples. That would probably mean that John was about 25 years old when Jesus selected him to be one of his disciples.
Whether 18 or 25 years old, It is certain that Jesus did not choose a whole bunch of 40 or 50 year olds as his disciples. He chose young men. And to me, that’s a great encouragement.
What about you?