Children are treated different from adults because we are aware that their brains are not developed at the same level as ours. Therefore, we have made laws and recognized these differences so we can protect our youth.
Christian Fernandez is a twelve year old boy who was raised by a teenager. His mother is now twenty-five which would make her thirteen when she gave birth to Christian. Sadly, it's probably not possible his brain is even developed to that of a normal twelve year old, who was raised by adult parents. It is not possible for a child to be considered an adult if the person who raised them is still a child themselves.
A twelve year old child should never be left alone with a two year old boy. "Boys will be boys" is such a common thing to say when a parent is told their child was fighting, and it's why most parents will not allow siblings to watch one another. Also, when a mother notices their two year old is unconscious, she normally will rush her child to the hospital and not spend four hours googling head injuries and looking up bank statements.
Christian Fernandez was acting on impulse when he pushed his little brother and he cannot be held responsible as he was never taught how to redirect his urges. Plus, he only knocked the child unconscious, if the mother would've rushed the boy to the hospital, Christian wouldn't be considered a murderer. Christian is not a murderer; all is he is guilty of is assault, being uneducated and underdeveloped because his mother was only thirteen when she became his mother.