Ethan had told him about a lot of things, he had emphasized how the warriors had warmed up to Iris and how she helped them to read and write. They saw her in a new light now, especially when the relationship between her and their alpha turned out to be so great.
Cane openly showed how important she was to him and it was not the first time for him to stay with Iris when she did not feel well. The Alpha even brought her with him almost wherever he went, even for the secret meetings.
Yet, Jace simply couldn't wrap his head around the idea that Cane took this relationship with Iris seriously, aside from him needing her because of the Blue Moon pack.
Not to mention the warriors.
They didn't state it bluntly, but definitely, Iris was not their favorite luna. If there was someone else, they would rather choose the other person than the daughter of Gerald, because seeing her brought back a lot of bad memories.