Besides gender, whne do you use ich and je? I keep getting onw of the exercises wrong because i use je but the xorrect answer is ich. (It is either "i do not know them" or " i know them" and i cant remember which at the moment) i only use the mobile app so i have been able to figure out when to use ich and je
It is only about the (grammatical) gender ("je" can also be neuter singular, so knowing 'it'), so in sentences like the ones you mentioned, both should be equally correct and accepted - we have no context to decide what 'their' gender is.
This would change if you were to translate "Do you know those women? I do not know them", because we have context that tells us that 'them' refers to some women, so we know it has to be "je".
I would need to see an example in which someone (even me) claims that to see what the difference is, because "Czy ci mężczyźni je znają?" is the most natural word order to me. In fact I'd say that the version we don't like, "Czy ci mężczyźni znają je?" would have a similar meaning to what you say, as it sounds like "znają JE", "know THEM".