It depends.  Under the MBT, a unitary business group is:

a group of United States persons, other than a foreign operating entity, 1 of which owns or controls, directly or indirectly, more than 50% of the ownership interest with voting rights or ownership interests that confer comparable rights to voting rights of the other United States persons, and that has business activities or operations which result in a flow of value between or among persons included in the unitary business group or has business activities or operations that are integrated with, are dependent upon, or contribute to each other.  For purposes of this subsection, flow of value is determined by reviewing the totality of facts and circumstances of business activities and operations.  [MCL 208.1117(6).]

An individual that owns a controlling interest in one or more entities but is not otherwise engaged in a trade or business will have neither business income nor gross receipts under the MBT.  MCL 208.1105, 208.1111.  Furthermore, an individual not engaged in a trade or business has no business activities or operations which would result in a flow of value with, or would be integrated with, dependent upon, or contribute to, the entities in which the individual owns a controlling interest.  Thus, an individual not engaged in a trade or business is not unitary with the entities in which that individual has a controlling interest.

On the other hand, an individual that is a sole proprietor or owner of a federally disregarded entity, which under MCL 208.1512 is classified as a disregarded entity under MBT, or is otherwise engaged in a trade or business resulting in business income or gross receipts under the MBT, may be unitary with the entities in which that individual has a controlling interest if the individual has business activities or operations (1) which result in a flow of value between or among persons included in the unitary business group or (2) that are integrated with, are dependent upon, or contribute to each other.  MCL 208.1117(6).