When we were thinking about bringing home a sister/brother for Magnus, my biggest concern was whether they'd get along or not. Even before we made the decision, just the thought of the optential of rehoming the new pup broke my heart.
I'm happy to see you have support here at the very least and you're able to take some comfort. I'm sorry to see you're having to go through this and I really hope you're able to find a solution very soon. Good luck.