I think in that type of scenario, if mom and dad pass away and the kids decide to carry on the business, on their passing a deemed disposition of their assets at the last will of mom and dad, depending on the will, happens.
If a capital gains exemption is claimed on their passing, then those shares wouldn't be able to be transferred to a corporation; at least that capital gains-exempt value could not be used. Therefore, you're into the same scenario, in which you sometimes take on personal level debt to pay out the other siblings. There may be other siblings in the estate who aren't taking over the business.
The terms of section 84.1 are always a very big area of concern for us as practitioners, but also for clients—sometimes not even with regard to the use of the exemption, but just with regard to the specific sale itself, as Brian alluded to earlier.