Can an oral real estate agreement be enforced in Va if written agreement has been lost?

Probably not.  I'm assuming you din't record the contract, which means that the buyer had no way to know that you had an interest in the property.  As what is known as a bona fide purchaser for value, the buyer has the right to enforce ithe sales contract.  In other words, since the buyer did notthing wrong, your recourse is against your brother.  You probably can't stop the transacton, but may be able to get money damages from your bother and sister-in-law. An oral contract with your brother to purchase real estate probably would not hold up, since contracts for the sale of real property are required to be in writing.   There are some exceptions where the parties are fiduciaries to each other, and brothers could be considered fiduciaries, but it's a long shot. However, you don't have an oral contract, you have a written contract.  The fact that it was lost does not mean that the contract was in writing, although obviously it will be much harder to prove that you had a written contract if you can't find it, but  there could be ways. For example, your brother may just admit it, and defenda on some other ground.  Or you may have an email between you and your brother referring to the written contract.  Or some other way.  It's a long shot, but not completely impossible.