Controlled Group, Affiliated Service Group or Multi-Employer Plan

I will be setting up a combo Cash Balance/401k Plan between 2  companies and am not sure whether this will be a CC, ASG or Multi ER plan.  The business structure is as follows: 

Company A owned by Brother and Sister 50/50.  5 years in operation

Company B is owned by Husband and Wife 100%. 20 years in operation.  The owners of Company A are the adult children of Company B.

Company B has 1 non-owner employee

The two owner groups take W-2 pay from each respective owner company.  Beginning in 2024, the parents of Company B will draw W-2 pay from Company A

Company A wants to set up the 2 plans with Company B the adopting employer.

Is this considered a controlled group due to attribution or is it an ASG or multi-ER plan?

The type of business is Property Management and they are affiliated with one another.

Thank you for any guidance you can offer in this situation.

Looks to me like a multiple employer plan where each company will have to pass the non discrimination testing. 
 

Brother and sister ownership doesn’t get attributed between themselves. 
 

For adult children the attribution would only go to the parent or child that owns more than 50% of the entity. That’s not the case either way here. 
 

I don’t see any attribution between A or B. 
 

So I’m not sure there’s much reason for these businesses to sign on to the same plans. What’s the advantage?

Agree with Bill, not a CG. Also, unless you have a management company situation I do not see an ASG here either as there must be some ownership overlap, which there is none.

Multiple employer plans do provide some cost savings in having one document for each plan, but you can't then operate as one employer so is it worth that savings for a situation that (in my opinion) makes the arrangement susceptible to administrative errors issues in making sure everything is run, calculated, contributed, reported and deducted as it should be?

Consider also whether a company that has no employee prefers a plan governed by State law or an ERISA-governed plan.

Thank you very much for your helpful responses.  You guys are the best!