double sinks continually back up
 

Why do my double kitchen sinks continually back up and into my dishwasher

Have you ever removed the traps under the sink to see if there plugged up?
While the traps are out you need to snake the drain line.
If the water can not get down the drain it has to go someplace.

the dishwasher drain line probably doesn't have a loop up high under the cabinet. post a picture of what is under the sink