I live close to sutterville, I started hearing about this story when I was a kid, and I've talked to the boys half sister who has searched for them for years. I think their dad has passed.
She's contacted sac pd they are pretty sure Norma and her kids had an accident and are in the river since it's right near normas place and back then there wasn't any barriers to keep cars from going in the water..
The sac pd said they don't have the resources to search the river for them and they are most likely not the only bodies in there, they basically told the sister that her brothers will never be laid to rest.
The sac pd never searched the river when they first went missing because they thought she ran away with her kids or left them with a stranger and fled. I contacted AWP diving team they can't help.