Q — I’ve always been wanting to write a story about the young Jesus set shortly after the events of him being found in the Temple at the age of 12.  However as much as I want to write this story, the plot I am considering is that the young Jesus is understandably grounded afterbeing found in the Temple, but is recruited alongside the young Mary Magdelene and the young Simon Peter (both also confined to their homes after commiting wrongful acts) to stop the Iscariot family from speaking at the Temple.
My approach is to depict respectively Jesus as a normal teenage boy who understands what he did was wrong but is bored, the young Mary of Magdela as someone who refuses to give in to her family’s demands but feels self-conscious, and the young Simon Peter as socially awkward, which, in turn, will be a reference to his behavior after Jesus speaks to him when he went fishing in the days following his resurrection.  My question is: How much creativity when writing a story about Jesus is too much?

A — I know that there is a great deal of interest in biblical fiction, that is to say imaginative stories written around characters and events in Holy Scripture. While I have done a fair amount of theological publishing, I have no experience whatsoever in writing biblical fiction. So, whatever I have to say will have very limited value for you. A major challenge confronting you will be the paucity of data concerning our Blessed Lord prior to his public ministry.

The episode of Jesus being found in the Temple in Jerusalem as a child is found only in the Gospel of St. Luke. The historical nature of that narrative is questioned by contemporary New Testament scholars, and it is often seen as primarily theological in intent. However, the real issue for you is that we know nothing about Jesus between that Lucan account and his baptism by John the Baptist as an adult. We can learn certain things indirectly by researching such issues as: Galilee at the time of Jesus (since Galilee is the region in which Nazareth was located), the common situation of adolescent Jewish boys at the time, family structures in Judaism in the first century, how the results of archaeology are shifting our understanding of first century Judaism, etc.

Perhaps by looking into some of these issues you might find angles that would help you develop your fictional account of Jesus in a fairly realistic way.
Where historical fiction — and I would include here biblical fiction also — is not based in actual historical reality it tends to lose a sense of authenticity. I hope these few remarks help.