[MyPemCharlie]

Well it is possible that Ein is being territorial about his crate only, like "This is my private area. Stay away." Especially if he is perfectly happy and comfortable with your brother and GF outside the crate. You know your brother's personality to know if he is the type to tease an animal, or the "love" animal type. If Ein is just trying to protect his area (crate) you might try having your brother/GF approach his crate with cheese or other tasty treat so that Ein associates your brother/GF closeness as a good thing.