I have been contemplating Luke's story of the rich young ruler in Luke 18. Might he be a young Theophilus? Some notes:
1. A priest (like the lawyer of Luke 10) would no doubt have been well-versed in and in full compliance with the Law. If Jesus had a conversation with a young member of the priestly family, the Law would no doubt have been a point of departure, conversationally.
2. The ruler's response (18.23) seems odd, as though he is unable to relinquish his riches. This would certainly be true of a member of the high priestly family, he himself expected to reign someday.
3. Jesus concludes the pericope with a statement of leaving family (18.29-30). If the ruler was of priestly stock, this admonition would have hit home deeply. So far as I can tell, though Jesus addressed this comment ot Peter, it still was a public statement, within the ruler's hearing.
4. Luke 10.25-37 is a parallel event, where a lawyer approaches Jesus with the same question as the ruler: "What must I do to inherit eternal life?" Jesus' subsequent story of the good neighbor involves a priest and a Levite, both of whom are corrupt. Might this be an indication that that both the lawyer and the ruler are of priestly descent?
If the ruler is indeed our young Theophilus, perhaps Jesus' call to abandon his riches and family is what caused Theophilus to initially reject Jesus. If so, the Luke's inclusion of this story might be giving Theophilus' rejection of Jesus a new context from which to present Jesus to Theohilus.
I have considered why Matthew and Mark both include this story where they do not include other pericopes unique to Luke which have priestly significance, specifically of Theophilus' family. I think the safest response would be that these stories were handed down by other witnesses as well, and Luke, perhaps drawing from those accounts, recognized the significance of them, and thus included them, where the other Gospel writers did not see their significance regarding a specific priest.