Buying vacant land to build on and sell for a larger price indicates you intend to sell, not invest and doesn’t qualify for 1031 treatment. On the other hand, if you buy vacant land with the hope that the value of the land itself will increase, then you may be eligible to dispose of it using a 1031 exchange.
in a 1031 exchange, all the proceeds must go to buying replacement property that is also business or investment property (example: you can't use the money to buy a home for yourself) to completely avoid any gain. since these are separate lots if 1031 is available one of you may decide to do it and the other not.
if this interests you and you haven't sold yet consult a tax or real estate pro for all the rules that must be followed. Fail on just one, and the entire gain becomes taxable even though you no longer have the money because it was reinvested. Also, know there can be substantial additional costs involved with doing an exchange vs just selling.
