[dragonwriter]

> They would be free to business with whoever they want.

The separate pieces would not be able to engage in business together that constituted a combination in restraint of trade, because that’s illegal whether or not they are breakuo siblings. Breakups turn what used to be sole company actions into combinations, which, in and of itself, adds legal complications.

(Also, as soon as the ownership diverges at all, which will happen almost immediately, between the siblings, a lot of things that are problematic for market effects would also be breaches of fiduciary duty on one side or the other.)

And all of this leaves out the explicit targeted constraints that would inevitably be part and parcel of any breakup order.