If you mean letting the days go by without you interacting with them and expecting them to be lesbianized out of boredom, then I don't think so. At least, not in any reasonable amount of time. You need to raise certain hidden stats, like thirst and others like that, in order to make them smooch da cooch.
Once their stats are high enough and they like eachother enough, I think you have to at least ask them to get it on in front of you a couple times, and then let them thirsty for a while untile they decide to start hooking up with eachother. But they'll often call you to ask you if you wanna join.