Can a 6 year old boy start puberty before his 8 year old sister

Jst want to know cuz I think my step bro started puberty before me she been wetting the bed and it smells like urine

Oh silly, puberty starts either from 11 years old to 15 years old (for girls!!) and it lasts for 2-5 years. Your step brother isn't reaching puberty because he's too young and still a kid. He is just wetting the bed and not what teenage boys do, what we refer to as “wet dreams”.