you actually can to an extent. sometimes, some characters may or may not see you when you're having an intercourse depending on your choices and each of them may react differently but you can romance them all, except othra/roushk because you have to cose one of them. the ones who reacts to you having a harem(as far as i know) are logan, rhot reacting to you with roushk, and bernard reacting to you with caleb.