Two Bronx women could do nothing but stare outside a local precinct on Thursday afternoon after being charged with a heinous crime: the murder of their 16-year-old autistic son and grandson, allegedly by starving him to death. Denise, the teen’s grandmother, and Geneva Jarvis, his mother, are accused of allegedly depriving Adonis Jarvis and his twin brother, both of whom are autistic and nonverbal, inside their home on East 147th Street between Brook and St. Ann’s Avenues in the South Bronx. Both suspects were silent as detectives walked them out of the 40th Precinct stationhouse on July 30. Police said the 16-year-old victim and his twin brother had been brought to Lincoln Hospital’s Pediatrics Department seeking treatment on or about March 19 of this year. The teenager’s twin brother, however, would recover.