If those newly arrived knights are from the dukedom where Orc Prince is being sent to serve a stud, obviously the knights would be glaring at him. It's their task to protect the duke and his family, yet the infamous Orc Prince is going to be married with the duke's daughter. They probably anticipate the duke's daughter will face a sad life of an unhappy marriage with a horrible man, just for the sake of getting foreign royal blood into the family line.