This is Mogoth, Steve's older brother.
Mogoth -unlike Steve- isn't autistic, and sometimes struggles to understand Steve's behavior, but He's very supportive and will do anything to protect his little brother.
Fun fact: the name "Mogoth" comes from the combination of "moth" and "goth".
I wanted Mogoth to me a goth moth but...as I developed him as a character he deviated from that early concept.
I kept his name because I still think it's pretty cool.