My grandparents purchased 3 pieces of property with one common backyard over 50 years ago. At that time, they are able to separate one of the homes on a separate deed; however, the other two shared one lot and remained on one deed.

My question is: Can both houses be left to two separate relatives upon my uncle's death or do they both have to be left to the same person? And if they are able to be bequeathed to separate people, how is that done?

I think you best bet is to have the property subdivided.

You have 2 choices: (1) you can have the property subdivided so that there are 2 separate lots, each with one house on it; or (2) you can have a deed prepared transferring the property to both relatives, with a separate recorded written agreement stating that each relative is entitled to one house.

Either method will work. However I strongly recommend that you go with option (1) because it will be much easier for each of the relatives to sell their houses in the future. If you go with option (2) then there will be problems selling the houses in the future since there will still be only one lot.