Convert 3 ways to 4 way Wiring
Smart Switches to the Rescue
You might be able to use the existing wiring for 4-way switches. But a simpler solution, and one that does not require any new wiring (just reconfiguration of the existing wires and new switches) is smart switches.
There are many brands and many different types. You will need to do your research carefully as there are different requirements for neutral &amp; ground and possibly other things. But basically, you should be able to:

Install a &quot;master&quot; switch where power comes in from the breaker panel (likely the 2-gang box, but not 100% certain without more details)
Install &quot;remotes&quot; at the other 2 locations. Depending on the brand/type, the remotes may use AC power themselves or they may be battery powered (with long-lasting batteries).
In addition to controlling the lights with the 3 switches, you can also have (if you want) options to control via WiFi or other means.

Make sure to get UL-listed (or similar listing, CE and FCC are not equivalent to UL) devices. Since at a minimum the master switch will be attached directly to 120V (or 240V, depending on your location) power, safety is very important.