The Davis Brand

Back when bodily functions were a regular topic of discussion on the playground, farts were said to have a specific "brand", that brand being your family's namesake. For instance, everyone in the Thompson family has the same brand of farts. They all smell the same. So I'd like to pose a question. Do family brandings come about because of genetics - same makeup of bodily acids and other digestive fluids... or is it simply because those in a family unit generally eat the same foods? Before getting married I was sure it was because families eat the same food, which is different from their neighbors food. However, now that Steve and I have been eating the same foods (at least for dinner) for the last four years, I'm convinced it's genetics mainly, with perhaps foods as a very small factor. Why? I have never mustered a Gordon fart and still consider myself completely incapable.