Nope. For clairity, remove the 12V batteries and solar panels.
Solar charging amps and the 12V batteries are not relative to windmill charging amps.
If there is a 12V load, both 6V batteries supply current equaly.
The windmill charges 1 battery. The other goes dead.
"like having two air tanks connected by one hose"
If current flows from the charged 6V to the dead 6V, that is a load and will make the dead battery... well, 'go more deader'.
Now add the 12V and solar back in.
The solar amps are charging both 6V batteries equaly, so it has no effect on their imbalance.
If both 6V batteries are the same voltage, the windmill is doing nothing of any significance.
See GeoM's post starting with "Flowing power..."
G-