Herod Philip I was really Herod Antipas" half-brother. [1] It was unlawful for Herod to marry Herodias because their marriage was incestuous since Philip was still alive (cf. Leviticus 18:16; Leviticus 20:21). Antipas had converted to Judaism, so he had placed himself under Mosaic Law. [2][source]
"We behold in John an illustrious example of that moral courage, which all pious teachers ought to possess, not to hesitate to incur the wrath of the great and powerful, as often as it may be found necessary: for Hebrews , with whom there is acceptance of persons, does not honestly serve God." [3][source]
"Not even the royal house was exempt from the call to radical repentance." [4][source]