>>63818575
Chiefly for duelling and martial arts, and typically in the context of carrying a shorter blade in your off-hand for parries or catching your opponent's blade, though two longer blades is not unheard of.
It can be argued that you can extend the usage beyond duelling and sport to say Italian streetfighting, but it would not be a normal on a battlefield.
So typically not two swords, but the combination of a sword and parrying dagger is attested, though so is a lot of other choices of sidearm, some more realistic than others.