For all the Wards at least, yes. The way the harem dynamic works in this one isn’t a traditional harem for them, but more of a polycule. Each of them that joins the relationship will be in a relationship with both you and Cerys, not just you. Anwen and Aine will be more like Cerys though and probably not have a relationship with each other cause they’re related (Anwen and Cerys are cousins, with Aine being their aunt).
Yea, I should’ve been more specific that’s my mistake. While the wards are going to be in a relationship with both you and Cerys, that doesn’t automatically mean their relationship with her will be a sexual/romantic one. You’ll be able to make the choices for those between the girls to be platonic/familial if you want instead. We’re already seeing how that starts with guiding those other relationships in the Ch2 part 1 release out now with Patrons.