Well, he admits it to Billy. What's neat about that is that Billy admits the same thing. They have the "hots" for each other. Early days, though.
In such emergencies, certain things do not matter. It's only afterward that they might come into play. But consider, even if young Justin tells his older brother that yeah, they were the poofters that he saw in the shower block, they just saved his life! Do you seriously think the brother or the parents are going to care about that?... At least, not in the immediate future.
About that brother... We don't know enough about the family to know if they are residents or holidaygoers.
I guess we need Chapter 2 to tell us more!