It’s great to read that you’ve decided to open your family to two adorable rabbits! You are correct — baby bonds are not enduring and will change at the flip of a coin once one of them starts being influenced by developing hormones.
I want to also point out that it is very possible one of them is actually a male. Sexing baby rabbits is notoriously very difficult, and many litters have happened because of a mistake in early sexing.
Do you know what their exact age will be when you get them?
I think perhaps for the transition of moving and coming to your home, maybe a few days or a week or two (depending on their age) would not hurt, but following that, you’ll want to separate them with a little gap between the pens (rabbits have been known to mate through cage bars!). That being said, separating them immediately would be the safest best. You can observe how the rabbits react to moving and make a judgment call based on this as well.
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.