It’s not going to work. First off, twin swords (with a full blade extending off both ends of the grip) aren’t real. It’s not that no one came up with the idea before, they simply don’t work.
Bifurcated blades do exist, but rarely on swords. The most common, historical, examples are varieties of swordbreakers, which were heavy daggers designed to trap and hold an opponent’s sword. The overall design is too fragile for a longsword, and wouldn’t survive use.
A number of modern weapon shops do sell twinblades and bifurcated swords as showpieces, because they look cool (if you’re into those aesthetics). But, they’re still not something that would see actual combat usage. You sacrifice too much utility for flashy options that you couldn’t use effectively in combat without getting killed. Swords are kept inside the body’s profile to make them harder to track and defend against. If you’re whipping around, waving it like a staff, that makes them easier to parry, and harder for the wielder to defend against incoming strikes.
There’s another big problem with this plan. Forging metal weapons isn’t something you simply learn, and can then make whatever you want. It is a process of technological development. It starts with smaller weapons, and gradually, as the techniques develop, becomes more complex, and able to support larger and more elaborate weapons.
Just to be clear, either variety of dual bladed swords are extremely complex from a forging perspective. Modern smiths can make them, but they’re standing on the shoulders of millennia of metallurgic and forging innovations.
In a setting where the metal your smiths would be working with is exceedingly limited, to the point that they’re not even using iron tipped spears as their basic infantry weapons, they would not have the raw materials to screw around and develop more advanced smithing technology on a whim.
Advancing swordsmithing (as a technology) would be extremely expensive, and not something that most smiths could afford to engage in. This means that smithing technology would progress very slowly, assuming it didn’t stagnate entirely. It’s not unreasonable to assume that iron would be in such high demand, that it would be illegal (or deemed a sin) to misuse the stuff (when experimenting).
This means: Forget twinblades, it’s entirely possible your setting doesn’t even have longswords. Depending on the availability of iron, they may be limited to something like the gladius.
The second big problem is, you’re dealing with people who have polearms. Even if it’s just normal staves, they’ll have more reach than your character. Meaning, they can get in and poke him without fear of retaliation. Even if they’re just using treated wooden spears, that could quickly get very messy for him.
Ironically, staves and polearms are the best melee weapons for crowd control. The strike patterns can create a wide enough arc, that it becomes much easier for holding multiple foes at bay. If you’ve never seen them, I would recommend looking at spear and staff forms on youtube.
Depending on the available materials, you might even see some kind of stone tipped spears. Not, necessarily, paleolithic designs, but with carefully constructed mounting mechanisms. Bronze or copper are also possible weapon materials. They’re softer, and you can make bronze or copper shortswords. So, if that material is available, it’s possible their swords (and spears) use that as their primary metal. It’s also (I’m told) much easier to work than iron, so there’s that.
So, there’s your logic check. There may be ways to rearrange this to get what you want, but you’ve specified will fundamentally alter the available weapons technology, social, political, and religious development, so it’s something you probably want to think through carefully. To an extent, this part is on you, it’s your setting, so you do control all the factors. But, try to keep in mind how people, particularly intelligent ones without access to all the information, would behave, and shape your world to fit that.