With small and medium-sized companies, multiple plans operated by multiple owned companies that are part of a controlled group, usually create a huge mess.
There may be a reason why similarly owned companies may operate more than one plan, It’s important to realize what that reason is. Sometimes, there are multiple plans for apparently, no reason. In addition, there may be companies that haven’t formally adopted a plan that they participate in.
As a plan sponsor, you need to identify the plans you have, and the companies involved. Too often, these situations lead to a tangled web and it’s your job to untangle them.