Herodians, like most political animals, strove to be "all things to all people". Saul cum Paul was trained as a Pharisee, but like the later Josephus who also identified with the Pharisees, this did not mean that he could not also be a member of the royal family.
There was considerable dissention in the family of Herod, as was typical of royal families. The source would have been the pursuit of political advantage rather than spiritual correctness and zeal.
The claim of Paul that he was of the tribe of Benjamin was also a political statement. The disciples of Jesus were promised 12 thrones over the 12 tribes of Israel. As rulers, each was expected to assume the name and identity of a particular tribe and the role of the corresponding son of Jacob.
© Charles N. Pope, US Library of Congress. All rights reserved.