The words concubine and harem didn't sit well with me.

I mean their society is very sexist during the old period, as well as she cant be a knight forever of course. I think he didnt mean harm and only meant so they could be together even if they cant marry or have a knight relationship :(

Well, in medieval period it's understandable he couldn't make her an empress and have a monogamy marriage.
Kingdom marriage needs to consider political gain as well.

I know but when you think about it the only child that is the successor of the throne will be the son that the empress gives birth to means that he needs to sleep with them but that hurts my heart you know.