Brilliant that you have made highways for the hogs – just what they need.
It seems unlikely that two adult males would share a house. I wonder whether they are youngsters, possibly siblings. That would be my guess. All adult hogs are solitary, other than females with their young. Are you absolutely certain that they are both in the house at the same time. They do sometimes alternate use. Males, in particular, are inclined to move nests fairly often. Also possible that a youngster could sneak in when an adult is sleeping, but I would have thought that was more likely in the winter, when the nest is likely to be more substantial and the adult less likely to notice if it had begun to hibernate.
Are the the ‘suspects’ those shown on your photos? It isn’t always easy to tell from photos, but it does appear that they are fairly young looking.
Anyway, really good that your hog house is being used! Good luck with them all.