Hassel has a similar hairstyle to Adaman with Irida's hair color and he has Adaman's eye color which has been established as a way to tell relation in previous Pokemon games. It's also said he comes from a long line of dragon trainers from an unknown faraway region which could potentially be referencing Hisui and the legendary Pokemon both Adaman and Irida are obsessed with are dragon type. It's an out there theory but Hassel's one of the only characters in gen 9 that references his ancestry and Adaman and Irida don't have descendants otherwise which makes them unlike most other characters from PLA.