Is your snake captive born, or wild caught? Many times, wild caught species will go off feed in the winter, as if they are hibernating (brumating). What are the cage conditions like? What are your temps? There could be a chance he has an infection or something similar.
Ah-ha! I just re-read your post, and see that he is not wanting to switch to rats. That may be your problem. Some just don't want to switch! what size prey are you offering? You may want to try a small rat, and see if he will eat that. If not, you say he is big, so I would not worry about it too much. He will eat when he is hungry, assuming there are no medical issues at hand. BTW, you need to find an exotics vet near you. He may not need a trip this time, but someday he might...it's nice to have someone "just in case".
As far as the housing issue, you need to keep them quarantined for at least 30 days. If one is sick, or carries
mites, etc., then he could pass that to the other one. Aside from that, many people swear up and down to keep them housed seperately, usually because it is easier to keep up with thier habits and bowel movements. I personally have always kept mine housed together, and have yet to have any problems. I seem to think they actually enjoy it!! Your boas are close enough in size that you would not have to worry about one of them squashing the other.
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