what in the bl trope is this l

I genuinely thought the story changed to yaoi with how the third prince acting like that

Hahaha it’s not like that. I read the novel, he is just reeeeally obsessed with his missing brother because he feels guilty (his brother saved him and “died” in the process) and he thinks if his brother got older he would be as strong as Prince.. so in a sense he is not lying, he does find him a good replacement.