Miguel Carrasquillo saw a lot of things growing up in a rough neighborhood of Chicago. He turned them into music.

“He has books and books of lyrics going back to when he was 13,” said his sister, Angela Martinez. “We struggled through childhood and he wrote about it.”

His rap moniker was Proliphic, a play on the word prolific.

“Look up what prolific means,” his sister said. “That’s what he was to me.”

Carrasquillo, 25, of River Grove, Ill., died Aug. 9 in Baghdad when a bomb detonated near his vehicle. He was based at Fort Stewart.

After his mother died, Carrasquillo took care of his younger sister and brother, always insisting that they go to school, said his sister, a sophomore at Columbia College.

“He was our Mom and our Dad,” she said.

Carrasquillo dropped out of high school in his junior year and later received a GED. Then he made his...