If they sit. It could be rust
The early disc brakes and some that were delivered from the factory were about 3/16" thick at the center where they are splined and fit the hub. These squeal like a banshee, the replacement OEM parts are thicker there and eliminate the squealing.
The drums squeal, don't stop well, and are just generally a pain in the ***...
drum or power brakes? Either way, tear down and inspect.