I'm assuming it was more or less a political/contractual marriage and in those scenarios I'd imagine both parties fulfil their love/lust separately.
I don't particularly blame either of them if that's the case, though it would be ideal if they were up front about it BEFORE it happened (but then...
Wow am I glad I didn't start reading this.
Harem manga that end with 1 girl are the worst for me (even if I do like the "winner").
It gives me that NTR feel.