I own 100% of one CPA firm (“Firm A”) and 51% of another CPA (“Firm B”).

I’ve owned Firm A for 15 years. My CPA partner and I started Firm B, 3 1/2 years ago.
Firm A only works with clients in Michigan and does not do audits (I’m just not that detailed).
Firm B has clients in 6 states and the only work it does in MI is doing audits (in all other states, it provides audits, reviews and compilations and tax returns).

I’ve been making 25% SEP contributions for the last three years. The SEP was set up under Firm A. Firm A doesn’t have any employees other than me….It does have legit, true contract employees, that are paid by the job, work from home, paid the same amount whether they take 1 hour or 4 hours to do each job (small reviews) and meet all other contractor rules.
The SEP has a three year employment requirement.
My *current* financial advisor just found out about Firm B, and tells me that Firm B must now make SEP contributions (the same % that I make to my SEP) for my Firm B partner, since the two firms are a controlled group.

Are the two firms a controlled group? either an affiliated service group or brother-sister?
If they are, can I avoid the controlled group designation if I drop my % ownership to 50%? (which I think may resolve the brother-sister issue, but is there an affiliated service group issue?
The two firms don’t compete. Now, there are times when a MI client wants a review one year (from Firm A) and an audit another year (from Firm B). That’s rare, but does happen from time to time.
My partner makes a lot more than I do for Firm B, b/c he has a lot of guaranteed payments, due to the fact that he oversees all the work and I just do marketing (and I have the long-time industry experience). So his 25% would be a lot more than mine…which seems like it wouldn’t be fair.