That would depend on whether the same owner is selling both sides.
A contract to purchase can describe both sides, but the seller cannot be different people, just as the buyer cannot be different people.
It can also be written as two contracts with special language to make the sales interdependent (not to close unless both close). Be warned though, that savings are difficult to be had.
The title insurance is a large chunk as well as the loan charges, if any. Title insurance is fixed by regulation and it is unlikely you can save anything by combining the closings.
Loan charges, however, are a different matter. Your loan officer can help you see if savings are possible by combining closings, and usually there are savings.
Other closing costs, similarly, are dependent on what's entailed. For example, the surveys are usually separate and the surveyor would give you a break if there truly was less work involved.
Your Realtor can best explain the situation and what can be done.