Well technically you do not even have to be able to wield longswords with one hand, that´s a thing of old versions of D&D that many games copied later, so two longswords would be a stretch.
https://en.wikipedia.org/wiki/LongswordBut as others said there are features that allow you to do that and add your full ability to damage too. two weapon martial style and dual-wielder.
I do not know if it would be in the game but there´s also double weapons in the TT, like double scimitars (Like in Kotor and NWN1 games)
