Thanks to everyone for their advice a few weeks ago about our resident troublemaker, Mr. Sterling J. Stewart III. I believe it was either Chickie or Moi who suggested getting in contact with a cat whisperer, or really a cat behavioralist. Not that I did such a thing, but I did do some research on cat behavior online.
Our problems might be appearing due to Sterling being a hyper-sensitive middle cat who thinks he doesn't get enough attention or power. And not that we hadn't already diagnosed him with these attributes, but the articles I read said that instead of scolding him when in trouble, that is when he needs loving the most. So we've been going overboard on showering him with affection. To the point where the other two cats look at us like we have lost our dang minds and are starting to feel left out.
When I say Sterling is an insecure boy, I mean it. You can't give him enough attention for his satisfaction. But ... the plan appears to be working so far!~ Have seen him "marking" his territory outside but haven't seen it inside since we developed the "smother with affection" plan.
So he doesn't have to go be a barn cat somewhere else .... yet.