Phil,
you might go the the Victron website- they have very good instructional materials on camper electrical system design and wiring. I just finished building my second camper and made good use of them!
My understanding is that (depending on the configuration of the Battery Management System if any) your batteries should be identical in chemistry, capacity and age, or they won¡¯t consistently charge if wired in parallel. Even small differences in cable length between two will mean one discharges much faster than the other, especially at high loads, one may overcharge and one undercharge, and then cables can become overloaded as well. This will wreck them in time. I expect differing internal resistance if the batteries are not identical would be equally problematic. I am guessing from your voltages that you have a version of lead-acid batteries. If you have lithium batteries with individual BMSs you should not have a charging problem but discharging still may not be even.
Victron¡¯s wiring guide explains a lot of these details.
Also, this guy seems to know EVERYTHING about marine/camper battery setups (he installs and maintains them) and has great how-to articles:
Cheers
--
Daniel Day
Kitchener, Ontario, Canada
DanielD