Harem is a form of poly relationship if consent is present. It is just that these days, both parties have side relationships, not just one way kind of deal.
Historically speaking and in fiction, harems refer to one individual having many consorts. Sultans used to have male concubines too so it is not as gendered as one may think. There are anime harems with twinks in them too.(Straight dude with girls and one twink) I've seen reverse harems with a woman in the harem too.
So, just like sultan gets all the women, Iltak gets all the men. That is the logic here.
Either way, I just want Iltak to pick one. It's my preference.

Pls don't make this harem, PLEASSEE