Aha!! A (natural) two-queen hive!
two-queen hives are commonly used to enhance honey production per
given hive footprint.
It's thermodynamically more efficient for ripening honey and keeping
the brood warm.
If you keep a couple of boxes of honey between the brood balls, they
will coexist.
When done commercially, usually two queen excluders are used. One
above the lower colony, and one below the upper colony.
Entrances can't block drones from leaving; otherwise the wrongly
configured one will accumulate dead drones that can't be disposed
of.
With the high population of house bees and foragers, you may have to
check more often for hints they will swarm.
Packed hives are great for comb-honey production, and this is a good
part of the year to be producing comb honey.
They're notorious for wanting to swarm.
That's my 2¢
In Wally's book, one of his splitting scenarios results in a
two-queen colony like that.
At the end of the honey production season he just recombines them.
I forgot whether he lets the queens fight it out when merging them,
or whether the beekeeper kills off the older one.
ps.
I once split a colony. A few weeks later I wondered why one didn't
produce an emergency queen. Both were raising brood.
When I inspected each of them, I found a queen in each, each marked
with a different color!
How did I miss that before I did the split?