The family of the innocent Brooklyn dad fatally shot on a city bus was horrified to learn that the teen gangbanger charged with the slaying could face a sentence as low as 7¹/₂ years in a juvenile-detention center, even if convicted on the top count.

Kahton Anderson, 14, allegedly opened fire aboard a B15 bus last Thursday, killing passenger Angel Rojas, 41.

“I’m in shock,” said Josie Guerrero, 26, a cousin of Rojas’ widow.

“I know his wife won’t be happy, because if there is one thing she’s been asking for, it’s justice, and this isn’t justice,” the cousin said.

“Angel doesn’t get to have a sentence; he’s dead forever,” she said.

The father of the suspect apologized to the Rojas family but also defended his son, a member of the Stack Money Goons gang.

“My son ain’t no killer like that. He was defending himself . . . he’s feeling sad,” said the dad, who wouldn’t give his name.

Cops said Anderson was firing at a rival gang member.