Re: Terminating Two conductors
I don't know a lug manufacturer that has a UL listing that allows is. In the larger compression style lugs its only one cable per opening.
Now, if I were to take a guess that lug is attached to a device such as a breaker for example and breakers usually have other lugs with cable combinations as you may need. In other words consider changing the lugs.
If I remember correctly lugs fall under UL486 which require heat rise and pull tests when used with a given cable(s). To attempt to apply cables other than those listed would violate no only the UL listing but the NEC of stated in art 110.