The teenage boy who murdered his two-year-old brother could become America's youngest ever 'lifer' after being charged as an adult.

Prosecutors want to lock Cristian Fernandez up for the rest of his life, reports Daily Mail.

Fernandez allegedly beat his younger brother David Galarriago to death at their home in Jacksonville, Florida, in March. The little one died from a fractured skull that caused bleeding on the brain. David died two days after being admitted to a hospital, said the daily.

Fernandez had previously assaulted his brother and broken his leg.

The prosecution says it wants to protect the 'public from this young man' and recommended that the 12-year-old face trial as an adult after reviewing his history of violence and behaviour.

However, Fernandez's defence has compiled a dossier exposing family turmoil, sexual battery and an abusive stepfather’s suicide, the paper found out. His mother gave birth to him when she was just 12-years-old. Fernandez’s father went to prison on sexual assault charges after impregnating his mother.

Documentation also indicated that abuse was a regular occurrence in the home from the beginning of Fernandez’s young life, the paper added.

Fernandez' stepfather apparently shot himself in front of the family to avoid being arrested on child abuse charges. However, two forensic psychologists who examined him found him to be reformable despite a tough life.