Winter is hard on hive colonies and for various reasons you may find yourself with a a hive that has insufficient bees to keep alive through the rest of the season or maybe it has become queenless. If left alone you will lose the bees that are there.
The only option here is to merge it with another hive. Note – Thoroughly check to ensure it does not have AFB before merging.
Do this on a warm day if it is in winter. Open up the weak hive and ensure that the bottom of the frames of the brood box are clean so as to sit on the top of your good hive. If there is a queen remove her.
Remove the lid and hive mat and clean any burr comb off the top of the frames. Place a sheet of newspaper over the top and then place the brood box on top of the newspaper. replace the hive mat and lid.
Leave the colony for a few days to sort itself out and soon you will see the newspaper being removed. When all is back to normal open the hive and sort out the frames to ensure there is sufficient food and the brood frames are together in the middle. You may need to remove the top brood box.