I doubt Hughie Fury's chin is anything better than his cousins. But he is tall and fast with his headmovement just like Vitali Klitschko were. Thus not getting hit too much and too hard to go down. People often overlook the whole package that guys like Vitali and Hughie posseses and mix it up with 'chin'. It goes the other way for small fighters such as Chisora etc. He might actually have/had a better chin than Hughie or Vitali.
I've always considered guys with good recovery powers to have good chins. So while some consider Fury's chin poor for getting dropped by Cunningham, I'd consider it strong for recovering.
Hughie Fury doesn't belong on this list. His 3 best opponents were Parker, Pulev and Povetkin Parker is featherfisted, he never stopped top-50 HW in his whole career. Pulev isn't a hard hitter, and he hurt Hughie in round 12 with right hand. Povetkin didn't land many shots, cause Hughie played it safe (as he did vs Pulev and Parker too). Hughie's chin is untested due to lack of hard-hitting opponents and safety-first style.
This should be said for Vitali Klitschko aswell. How many crisp power punches or combinations did his chin actually take from Lewis, Sanders etc? Just a few here and there. Chin was not tested enough thus overrated in my honest opinion.