He is the chairman/owner of Worldwide Pants. I guess maybe he couldn’t be fired, but he could probably resign and appoint someone to take his place. I’m not sure if there is a board of directors or how much power they might have since it’s not a public company.
These affairs are not illegal. These are two consecting adults. It’s pretty common to date and/or marry people you work with. Sexual harrassment is a whole different issue.