Brother Bob's oven went through a house fire. Are they toast or can we clean them and re-season them?

You bet.. Clean'em up and get cookin.

Dutch ovens are often used over open fires so it should be ok. The last time I had to clean soot off one I used baking soda. Worked well. I hope yours is ok. They are very amazing, versatile pots.

If it's not melted it should be fine. I would take a wire brush and clean it real well, then re-season it and you're GTG. I have 4 cast iron pans that I found covered with rust next to a dumpster. They're all black and shiny now.