Electronic – Utility of two pins requiring same voltage

I have no experience with the processor mentioned. The following statements should be true in general unless specific indications to the contrary are given in the data sheet. The following does NOT answer your question with certainty for your specific part but does tell you what may legally happen if you ignore the issue.

If a port exists then the related gates need to be dealt with, pinned out or not.

If the manufacturer provides a power down ability for the port then you can expect the incremental drain to be "in the noise" compared to other processor currents.

If the port is powered but not pinned out then either
the design assigns it as outputs, or as inputs with pull downs or pull ups,
OR you need to deal with it explicitly. If the manufacturer defaults it to some "safe" state you'd hope that the data sheet says so.

If set as terminated inputs (high or low) or as unloaded outputs you'd expect the incremental current to be low - look at figures for active ports for the processor concerned and you'd expect the same or somewhat less (no multiplexer path to pin active).

If set as unterminated inputs (by you or the manufacturer) then current drain can be anywhere from minimal to fatal - a drifting input pin can float to about Vdd/2 with the input gate in the transition state between high and low and an unknown and significant current following the "shoot through" path. The exception are Schmitt input gates whose inputs will behave properly and sit at one or other rail.

While you would hope that an active input gate, that has no multiplexer path to a pin, will be pulled consistently high or low by interior bias current that the design applies, this is not guaranteed and Murphy is allowed to assign such an internal uncommitted input to whatever voltage is worst if you don't beat him to it.

As user alexan_e said in the comments, you've got these problems because your analog input pins are floating.

Never leave any input pin floating if possible. With digital I/O this could lead to increased power consumption. This problem does not show up with analog I/O, nevertheless you will run into other troubles like the one you described. Have a glance of this question to see other reasons to avoid letting input pins floating.

What I suggest you is to all your inputs, especially the ones you care about, have a path to a known voltage through some resistance—often, a pull-down resistor is the answer, but that typically depends of what you're trying to achieve. How big is this resistor depends of the impedance of the driving circuit and noise, but usually something between 10K and 1M ohms; lower values are good for noise, higher values is good for maximizing input impedance and low frequency response for AC-coupled circuits.