They were most probably under the age of 18.
Most of Jesus' disciples were under the age of 18, with some as young as 15.
As there is no indicator in the Bible of a specific age of the disciples, it could only be established<em> through historical context.</em>
Peter was the only one married disciple. A Jewish man received a wife at the age of 18. All the others were bachelors, thus probably teenagers.
Most of them were apprentices to a trade when they were with Jesus. Education of a Jewish child concluded at the age of 15.
Judging from these pieces of evidence, they were between the ages<em> 15 to 18. </em>
