Oh, there's an easter egg? I didn't even notice, though i haven't read The Crossed in years so i probably forgot it. The Crossed-Badlands had a lot of short stories that tied in what happened around the world. I thought it was going to be similar from all the Nude Zombies i saw. Wait was that the easter egg when they joked about him picking the nude Female Zombie as a blockade so he could do lewd things to it? If not Either way I'll try to spot it as I'm currently trying out different options with saving that girl in the closet at the mall.
Also I'm fine with the harem setting since it's intended to be that way. I didn't dislike the sister to begin with, i just thought if you chose certain options he wasn't going to attempt to be with her from a dialogue point of view.
Example when you talk with the mom in the kitchen about joining her on the scavenging or staying to bond with your Sister, i thought the going out meant you didn't want to fix it with your sister as she was the topic of discussion prior to the choice. I think it was just how the dialogue was worded that confused me.