Aaaaaaand no one thinks to offer an answer other than it's in the wrong forum? Awesome.
Anywho, my understanding is you can either use a co-op partner to help you with this or you can go to the whorehouse in Bowerstone Industrial and use the options with the right bumper to invite a prostitute to have sex with you - do this for a few of them and they should all join you. I've never done it myself because I have never needed to (I'm not interested in the weapon that requires an orgy to upgrade it) but if someone else here has actually managed it then they can help you out more than I can