Before describing my problem I’m giving you little bit background. We had love marriage one and half year back. Now my wife is pregnant. My wife family is joint family.
Yours is surely a unique problem. But I commend you for the fact that you have the courage to accept that you may have selfish motives here. It takes a lot of guts to admit something like that so kudos to you!
Now coming to your conflict, this problem can only be solved by open communication. I would request you and your wife to put your egos aside for one day,go away to a nice quiet place and sit and talk your heart out over this. Maybe your wife is not able to see the love behind your selfishness. Maybe she is not able to understand that you don’t want that kid in the house because you want your time with your wife and your new baby. And this may be because you haven’t been able to convey this love to her properly. Set aside a day just for the two of you, show her how much ou care and explain this to her.
On the other hand, although she may be very attached to that child and wants to do good by him, she must understand that keeping someone else’s child is a very very big responsibility. Its a different thing to live in the same house with a relative’s child and to have the child under your responsibility for 24 hrs. Especially once your own baby comes her responsibilities would grow a thousand times and then she will get frustrated.
Try and explain this to her. Even then if she doesn’t understand , what you can do is tell her that you respect her wishes and are willing to give it a try. But also tell her that if she ever wants to go back on her commitment and send the child back you will respect that too. But she should feel free to share her feelings with you. In this case if the responsibility feels too much to her, she knows that she has your support.
This will strengthen your bond as husband and wife and she will know that you are there for her no matter what.
I wish you all the best!