When you bought out the other siblings, a capital gain situation occured already for them. They should have filed capital gains tax.
Unforutnately there is no way to transfer this property without incuring a capital gain unless it is sold at a loss or gifted.
You can defer capital gains if you do it as a like kind exchange.
To convert the shares to actual land, you have to dissolve the organzation. If you dissovle the organization, the land is distributed according to pecentage of shares.
If you were to dissolve the corporation as discussed above, the corporation would be required to report the transaction as if the property had been sold at its current fair market value and then the corporation would be subject to tax on that gain (even though it did not actually receive any money).
A more complicated but less taxing transaction would be to do a corporate split (reorganization) with each corporation retaining the appropriate land parcels. That would put each of you in control (by virtue of corporate ownership) of the land tht you want without generating a current tax liability for either the corporation or you individually.
Without knowing the dollar values involved, it is impossible to tell whether your situation merits the time and expense that would be involved but, if it does, ou should consult a knowledgeable attorney and/or CPA to assist in developing the reorganization.