Way back when we were still waiting for Red Dead Redemption 2 to be released in October 2017 (yep, we originally though we'd get this game last year), Rockstar dropped the news that it was delayed.

Little did we know this wouldn't be the last delay, but nonetheless, a series of screenshots were released alongside the announcement to make it sting less. Among these pictures was a masked bandit brandishing two pistols at once. Later we'd learn that the bandit was called Arthur Morgan, and we'd be playing in the game as him.
The dual-wielding feature also made it into the game. Back in Red Dead Redemption, John Marston could only dual-wield if he equipped the Twin Revolvers.
With Red Dead Redemption 2, Rockstar decided to expand the feature and let Arthur akimbo any two one-handed weapons. They don't need to match, either - you can sport a revolver in one hand and a shotgun in the other.
Red Dead Redemption 2 has a lot of interlocking intricate systems, and when it comes to combat, your holsters will be almost as important as the guns themselves.
Holsters unlock and define a number of abilities or stats. Specifically, you'll need an off-hand holster to unlock dual-wielding. In Chapter 2, there is a mission called "Blessed are the Meek?" which will reward you with your off-hand holster.
Once you've unlocked the ability, you can select dual wielding two one-handed weapons in your weapon wheel, marked by a Diamond and Club symbol. You can customize either weapon to your liking. Whether you want them to match or not is up to you.
When using Dead-Eye while dual-wielding, Arthur will give off more shots, increasing your chances of critical hits and headshots. When not in Dead-Eye mode however, dual-wielding comes with an accuracy debuff to compensate for the advantage of having a much higher rate of fire and combined damage from two weapons.
If you want to find some unique weapons to dual wield, check out our guide.