All I can do is relate my shelter experience with Pinot, which I've done, but each cat's case is different. I've never had another cat with this problem...
Pinot came from a shelter, her story is here: http://catoftheday.com/archive/2009/May/05.htmlBUT we were told by three vets not to have another animal in the house; that this was in all probability caught at the shelter, and Pinot would probably be a carrier.

Bottom line: a "URI" is not always a "URI" and each cat is different. The vet is the one who knows the story of all the kitties and needs to be the one to make the determination. Shelters are breeding grounds for this type of disease; it's unfortunate but reality. My personal opinion, for what it's worth, is that if Kiki's been having problems that were not mentioned to the vet, she needs a visit, and you need to discuss exposure issues regarding Desmond and Pippin. Let us know what happens; I hope all kitties are fit as a fiddle soon!