Demon Bull King
The Demon Bull King is Red Son's father. In "Monkie Kid: A Hero Is Born", it is shown that Red Son is extremelly loyal to his father and will do whatever it takes to make D.B.K. proud of him. Red Son was the one who freed his father and wanted to get rid of MK for him.
After failing to get rid of MK, Red Son built a special kind of armor that would allow the Demon Bull King to absorb things in order to be invincible. Despite everything Red Son does for him, D.B.K. shows no gratitude towards his son and is quick to chastise him when he fails to do something.
Princess Iron Fan
Princess Iron Fan is Red Son's mother. The two had little interaction one on one. Modt of the time she seems to be annoyed by his antics and possibly has a low opinion of him since she taunted him when the bull clones lost the staff again. However, Princess Iron Fan seems to care about him since she talked her husband out of chastising their son for failing to retrieve the staff.
MK is one of Red Son's adversaries.
When Red Son first met MK, he gained an instant disliking to him, stating that he ruined his family moment. After the Demon Bull King attempted to kill MK, Red Son stopped him, but only because he wanted to do it for him.
Red Son met Mei when she rescued MK from him, believing that they were just racing, Mei mistook Red Son for a friend of MK's and wanted to invite him to play video games with them until she found out he was DBK's son. After MK is presumed to be dead, they almost fought with each other had MK not arrived in his Cloud Jet.