combining hives

I am a new beekeeper with two hives. Each hive has two deep brood boxes. One hive is obviously much stronger than the other. It has nearly filled the frames in the upper box while the weaker one has only filled about half the upper box. Neither hive has put any honey in the ross round supers above the brood boxes. It has been suggested that it is too late to requeen the weaker hive now but that I should consider combining the two hives for the winter. Does anyone have any advice on this matter and how I would go about combining the four boxes? In the meantime I am trying to determine why the one hive is weaker to eliminate the possibility of pests or disease.

I would consider feeding the hives and hope they both can make it thru the winter.It sounds like your weaker hive may have enough stores if its fed.Combining the hives is just moving the frames of brood and honey over to the other hive.

rowtohoe, ross rounds are difficult to get drawn out. you must have strong colonies and a heavy honey flow. i would replace them with frames of foundation, or better, drawn comb. if you dont have an extractor, use thin surplus foundation or many times someone in a local club will loan one. sometimes local clubs will have an extracting "party". Your bees will put up at least 3 times more honey in drawn comb than foundation.
i dont know when your main honey flow is, but something usually comes in thru the fall.
(maybe not much durring the summer).
you can requeen anytime you want, but you may not see the improvement untill next year.
many beekeepers routinely requeen in the fall.
it sounds like they should both be strong enough to make it thru the winter, just keep check on the weight of the hives, especially next spring when there is lots of brood and not a lot of honey coming in (or many cold or wet days)
you may even try setting the smaller hive on top of the stronger one with a double screen between.
be sure to remove all honey supers before wintering.