Two Florida brothers were allegedly gunned down by their sister’s boyfriend inside her Miami apartment when they rushed over to protect her from him, cops said.  Gianni Pierre, 28, and his younger brother Jaheim, 23, were allegedly shot by Antwan Carter at around noon on Saturday after a scuffle broke out in the apartment, the Miami Herald reported .  The brothers’ sister had been dating Carter, 31, for around four years, but they were wary of their relationship.  Antwan Carter, 31, allegedly gunned down two Florida brothers who tried to protect their sister. Miami-Dade County Corrections and Rehabilitation They had rushed over to her apartment to “look after her” due to a “history of previous domestic violence,” cops said in their arrest report. Jaheim and his sister argued before he then struck Carter, who had interjected. The three men then became embroiled in a fight.…