I recently made one hive out of 2 tiny hives. "Canada" was a hive about the size of a honeydew melon. "Water meter" hive was the size of a large grapefruit. Together, they equal the size of one beautiful small watermelon with the potential to make oodles of honey and most importantly, survive next winter. I only had to figure out how to join the 2 without them stinging each other to death in one gigantic grocery store cage match.
That is where newspaper comes in handy. Canada was an already established hive. I caught water meter hive an hour before the sun set. I took wet newspaper and closed off one half of Canada by pressing the wet newspaper onto the sides of the hive until there were no holes for the bees to get through. I then put water meter hive in the back of Canada's hive box with a jar of 1:1 sugar water and closed it up for the night. The 2 separate hives could smell each other through the paper, but the only way they could get to each other was to chew a hole in the newspaper. This takes a few days and by the time the hives are able to get to each other, they are familiar with each others smell and usually consider the other family.
Here is the hole the bees chewed in the newspaper to merge the hives.
And then you know the rest... the 2 queens fought to the death and the winner was the new queen of Canada.