I agree that they were all brave, but I do not think they would have all ended up in Gryffindor. Antioch was selfish and wanted only to better himself, so I believe he would have been a Slytherin. Cadmus, on the other hand, was unable to betray the love he felt for his would be bride. This speaks of a Hufflepuff, but I feel he was also the one to lead them to that river in an attempt to confront Death, very much a Gryffindor trait. I believe that he could have gone into either house. Ignotus, the story tells us, was very wise. It does not call him smart, it calls him wise. Since all three were well learned in the magical arts, they would have all had to be smart. He also displays a great loyalty to his brothers when he faced Death with them, for he did not seek anything from Death. He would be unsuited for Ravenclaw as he did not want to make himself better than others, as he was called a humble man. He would have gone into Hufflepuff or Gryffindor for in his second meeting with Death, Ignotus met his gladly and went with him willingly.