Maybe he's angry because his mom likes Estelle better than his sister...or he's just obsessive like his mom...or maybe he was even linked to the magicians arc
Nope, spoiler uwu . . . . . . . The prince is just suspicious of Emel cuz Emel's family isn't on good terms with the Castiello family. I am pretty sure he thinks Emel is a spy or something like that.
Maybe he's angry because his mom likes Estelle better than his sister...or he's just obsessive like his mom...or maybe he was even linked to the magicians arc