here are some threads on moving someone in among other things. Admittedly mostly from our tribe, as we have just been through all this, but hope it helps... there are lots more if you do a search.
It doesn't seem to work for a partner to just randomly move someone in. It doubly doesn't seem to work to expect a partner to just love and find someone attractive that you do. Double whammy.
I'm not sure where your voice was in all of this. It sounds like you were looking for a unicorn and he has all the control... a bit like polygamy or a one penis policy (opp). great if you are into that, but it doesn't sound like you are so speak up. Tell her and him that she has to go and that they can conduct a relationship outside of your home on a balance of all your terms, not just theirs.
I suggest that you find your own partners in the future and leave him to find his. People are not pets and while its really nice that you think that you can take care of people and that they will just slide right in and be willing to be taken care of... they eventually have their own thoughts on what they want out of life and really it shouldn't be that big of a surprise. They have a right to what they need.
Sounds like you have some discussing to do and some changing to do... all of you. good luck with that... hopefully some reading here will help.