Mr. Amoeba, you have to get the hives out. They have to be physically removed. The first thing you need to do is identify EXACTLY where the colony resides before you or anyone else takes action. I haven't seen your set up and I know you said they're in the wall but you say you have a two story house right? On two storys they are rarely in the wall but in between the two floors or the soffit, eave. I'm not saying this is the case but it needs to be determined where they are. if you leave the hives, you will have issues that you don't want, to name a few: roaches, ants, rodents, honey dripping and staining, fermenting honey odor and other hives that will be attracted to your house like a magnate. Leaving the old hive in the wall is a not an option, unless the colony was very young, but this is usually very difficult to determine by most people. I had a lady tell me she had a hive that was in an area of her bldg for 2 days, but I wound up pulling out three boxes worth of comb from the area and I could sit here and bore you with other examples, but I won't do that to you. If I can be of help you can pm me or simply ask more questions here and we can all possibly help with you and your great uncle's situation. Let us know. Some typical scenarios:
The last one is one that was in a wall. You really don't want to leave something like that in your wall trust me.