Latching relay ??

one main reason for latching relays is that they only require power to switch states. normal relays continue to draw power in one of the two states, open or closed. For example a NO (normally open) relay will draw power all the time it is in the closed position.

Might be related to the current rating of the contacts of each relay. The latching relay with a lower or insufficient current capacity may be used to control a higher current-rated solenoid. This arrangement would also permit smaller gauge wiring on the control-side of the circuits. Wire gauge would necessarily have to be large in high current circuits.

Many times electrical engineers use a smaller "electronic" relay to drive a "power" relay (larger current - amps)

I do this on my model trains!

A latching relay draws no power after function is accomplished.
My guess for second large relay for charging goes through a circuit board that requires the charging system battery to be nearly charged before energizing that relay.
Yes, sometimes small relays are used for control. Doubt that a large relay would be used as control.

RV latching solenoids have a second small solenoid that mechanically latch the main solenoid in the on position and hence use no power, except when switching states. Typically used to turn off unwanted power like lights when you exit the rig. Prior rig turned off the refer (really dumb) and the current rig does not.

Typical charging solenoids are controlled by the ignition or smarter electronics and they are NOT latching solenoids.

I am not too familiar with TT house battery circuits but in my rig the latching relay is controlled by a SPDT momentary switch. The relay is used to disconnect the house battery entirely. The other solenoid is the Battery Mode Relay, when the ignition is turned on the mode relay engages through the accessory circuit of the ignition. When the start circuit is engaged, the accessory circuit is disconnected until the ignition key is returned to the run position. Manual control of the mode relay is through a SPST momentary switch on the dash and is used to Boost the chassis battery if needed in order to start the engine.

There are many different latching relays and the one in my rig only has one coil, the latch is operated by magnetism. It's pretty cool and simple but baffling until you reason it out.

They are performing two separate functions, the latching relay is a disconnect, the continuous duty is for charging or emergency start, depending on where the solenoid is triggered from.

There are many ways to use relays. A typical latching set up uses one relay to close a second relay. The second relay uses one of its contacts to feed power to its coil so it stays latched. This is old technology, many of today's relays are controlled by board mounted solid state devices.

Trying to determine the circuitry is part of the adventure for any electrical trouble shooting.

There are two relays because they do two different things.

The house battery is connected/disconnected from the house with a latching relay.

The other relay connects the house battery to the chassis battery for charging, or boosting in case the starter battery is low and won't start the MH.