Legal Question in Real Estate Law in California

It is absolutely possible, although may be unnecessary to your plans. You would need a knowledgeable real estate lawyer to dot the i's and cross the t's in processing a lot merger, but just like large parcels can be subdivided, two parcels can be legally merged. Before you go to the trouble and expense of that, though, make sure you need to do it. It is quite possible that in the distant future, when your apartments have run out of their useful life and are ready to be demolished, the two lots would be more valuable separate than merged. They certainly wouldn't be less valuable. So unless you have to merge the parcels in order to go through with your development plan, there's no reason to do it.

I agree, and would only add that building a permanent structure across two originally separate parcels might result, in some jurisdictions and under some circumstances, in an involuntary merger of the two parcels.