I think "They sleep without it" should be aceepted too, for "niego" can replace an object as well as a person. Am I not rignt?
It's not that "niego" being "him" has to mean a person (let's think of budzik - an alarm clock, it's masculine), but otherwise you are right, it's Genitive both for "on" and "ono".
sorry, why is niego used? would it be wrong just to say go?
edit: I did a bit of research using translate, niego is genitive form of on which makes sense because of the use of "nie". I dont know how other people arnt shaken by the use of niego here though, ive never encountered it before.
"bez" takes Genitive. Well, 'go' also is Genitive form of 'on', but it can't be used here.
The thing is, that "bez" is a preposition, and if only an "n-form" exists, it has to be used after a preposition. It cannot be used on its own, though.