I have said, many times and on many topics, that this is the sort of eventuality that points out how essential it is to make a plan.
Making a plan and putting it on paper lets you (and members of your group) go over it for holes, flaws, and what ifs.
Personally, I plan assuming many more people will be here than just me and my MAG. While my family live too far away to even visit often, one of my MAG members has lots of family in the area. I plan, therefore, for the possibility that things might be such that they will come here for aid/be invited here.
I have pointed out the guest thing many times on these forums. It is all fine and good to have your plan be "me and mine" until TEOTWAWKI occurs while your wife's sister and her family of husband and three kids is visiting.
This is also why I have what I call "give away bags". I have made up some very basic, BOB like sport bags as survival kits. I can use the gear myself, trade the contents, whatever; all without affecting my MAG and its stores of supplies. The PLAN though is to give them out to certain neighbors, friends, or the like that may come to me for help. There are people who might come and I don't want they to stay here (but don't want to send them away to die), or those who will (regardless of the danger) try to make it home to family etc...These are the people I make these kits for. I don't have a lot of them, and have no intention of being a mini-Red Cross, but I am planning in order to be able to help others.