The king is a polygamist
I'm sure you've played a game of chess and gotten the right to promote your pawn to a queen right? How do you think the first queen feels about the new queen coming in and stealing his majesty's love from her clutches?
I believe the king is a polygamist. While he has a happy marraige with his first lady, he goes out and marries a lowly peasent. A peasent!!! She is much more regal and beautiful and he just goes out and takes for himself some other chick that he thinks is "hot"! I mean really? Come on! Surely Mr. King you are better than that!
Well, I guess she'll have to live with it, or maybe find a way to sacrifice her to the enemy, then the king is all hers again. :)