This is for Ironrod/Kracken just in case.
If you're serious, you may want to contact your local Animal Control for advice. My understanding is most don't handle wildlife cases like this (only domesticated pets), but they could likely provide some guidance.
This Arlington, VA Animal Welfare League's site suggests a concoction to try to clear wildlife from an attic (not sure it applies to foxes per se, sounds a bit more about birds):http://www.awla.org/animal-control/wildlife-control/
Evicting Wildlife from Your Home
Here are some tips on evicting unwelcome residents. Before taking action, however, make sure that baby birds are able to fly and young mammals are old enough to be relocated by the mother. Your intention should be evacuation, not extermination.
For safetyís sake, donít try to remove an animal with your hands. The tips below are usually very effective, but if you donít have success with them, call us for advice or to ask about borrowing a humane trap.
In the attic
Ammonia works wonders. 1/3 of a cup in a shallow pan coupled with a loud radio and/or bright lights will prompt your furry guests to leave. If there are babies, give mom a few days to move them out, then find and seal the openings to keep new tenants from moving in.
Birds donít have a good sense of smell but are very sensitive to noise. A loud radio will make nesting at your house very unpleasant.
If you're in fact joking about your in-laws being in the attic and not going away, I don't really have constructive advice.
When I was about 13 (around 1978), two squirrels got into our family's house via the chimney one afternoon when I was alone, home from school. I kept using a flashlight to scare them off. Eventually my mom the teacher arrived home, and she instructed me to use a blanket to block off one aisle from our kitchen while she chased the two squirrels through the other aisle and out the kitchen entrance. I wish we had video of that.
Not that squirrels are all that scary, I just did worry about rabies and the like if they bite. I think they just wanted some peanuts...