If I myself had those 2 hives, I'd combine. I'd set the suspected queenless hive on top of the queenright hive, and remove all the hive and stand from the one that is removed. You say the one has little capped brood, is there any open brood or just hatched brood? If not, then it's probably queenless since 4 eyes or more checked it out. I'd destroy all queen cells and look thru it one more time to be as sure as you can the queen is gone.
I've been keeping a few hives for the past 20-25 years, and no longer treatment free as I got tired of the losses.