My robo hamster is completely vitious, he always bites. how do i get him to stop?

i had 2 robos originaly. grumpy bear used to beat up his brother, piper, when they were younger and ended up stunting piper's growth. he had a huge scab on his rear end one morning so i seperated them. bacause of this piper died at only 7 months old. piper was very lovable and i don't know why grumpy is so mean. i'm trying to find a way to calm grumpy down so i can just love him like i loved his brother. he has lots of space, including 3 cages that r connected, and they hold multiple beds, hideouts and toys, including 3 wheels, which he never used before his brother died. i gave him piper's old wheel and now he seems to love it although he doesn't run nearly as much as piper did. he has plenty of space to run around and is never in the same place when i look for him. he's very territorial and hates it when i go in there to clean up or feed him, he tends to scream. once in a blue moon i can call his name and he'll come to the edge of the cage and talk to me. that's the only time i get to see him. i aways tell him how much i love him and would love to hold him. but i don't want to scare him or make him mad. i really do love my little grumpy hamster, no matter how mean he is to me. i don't know what to do.