Sex without love or committment is a common phenomeneon these days so one really cannot say if the peeps as per meh nepali were cheating or not.  Only if the vows of commitment are taken then it can calssify as cheating...However, merely thinking about someone may not classify as infidelilty but if the person imagines "doing" the other person when doing his/her spouse, then obviously that could classify as cheating (as the person's intent is present).  As I always say, to each their own!