Ishmael Avive Santiago, 21, pleaded guilty to federal robbery and weapons charges and was sentenced Thursday to more than 11 years in prison.
Rahiem Moses Santiago was sentenced in March to more than 14 years behind bars.
Prosecutors said that the cousins conspired with a 15-year-old to steal a rifle, and then the men robbed a Walgreen's store at 11306 U.S. Highway 70 West early July 28, 2011. Rahiem Santiago, then 18, struck the female clerk with the butt of the rifle, authorities said.
Rahiem Santiago was arrested the next day after carjacking a woman and leading authorities on a chase, police said.
The 15-year-old was charged as a juvenile in connection with the Walgreens robbery.