If they are different legal entities and they are operated separately, the fact that they have common ownership is just not relevant.
Look at them individually and see if they qualfy for exemption. However, as I understand you, the only reason a CTR is necessary is because the deposits are made "by the same person;" the companies not cross the filing threshold individually. If that's correct, there's nothing you can do except file CTRs.
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In this world you must be oh so smart or oh so pleasant. Well, for years I was smart. I recommend pleasant.