Especially as a house rabbit forum, BinkyBunny’s view is that rabbits are considered truly bonded if 1) both rabbits have been spayed/neutered and 2) they have gone through the bonding process (https://binkybunny.com/infocategory/bonding/). Alongside this, rabbits who are intended to live together in the same enclosure must be bonded. If neither of your original pair are fixed, then the majority of the house rabbit online community will not considered them to be “bonded”, since hormones are a big piece that prevents stable, secure bonds between the vast majority of rabbits. Keep in mind that a neutered male can still impregnate an intact doe up to 6 weeks after the neuter.
Note that a baby bond is not the same as a true bond. A baby bond, also known as the false bond, refers to the relationship between rabbits where at least one is unfixed and young. Due to the absence of hormones, territorial feelings and aggression are not yet present, facilitating what can seem like a very loving, stable relationship — however, this can change very quickly once a rabbit reaches sexual maturity. Please note that rabbits being together since birth (i.e. siblings, parent-child) does not rule-out the baby bond phenomena, since rabbits can and often will fight and mate within family. Therefore, if you suspect your two rabbits have a baby bond, please keep them separated to prevent further pregnancy and potentially dangerous interactions. Also note that a female rabbit can be impregnated immediately after giving birth, so they need to be separated now if both your rabbits are intact.
Assuming all rabbits will be spayed/neutered, once properly bonded (over a couple weeks/months, as outlined in the link earlier), those rabbits should never be separated from each other, therefore, if you will now have three rabbits (the original pair + one child) and plan to have a bonded trio, they must all stay together — taking one inside then back out every day is not recommended. Please also note that depending on temperature differences, the act of constantly shifting a rabbit indoors to outdoors can be medically risky due to the rapid temperature fluctuations, in addition to the rabbit’s coat not staying in conditions that will facilitate the formation/maintenance of a coat which is appropriate for their living space (i.e., a rabbit who is outdoors to sleep overnight may shed its winter coat due to not being in chilled temperatures consistently due to the constantly being brought inside).
Until the bonding process is complete, all rabbits who are not bonded with each other should be housed separately to ensure all rabbits’ safety (presumably should be instilled after the baby is successfully weaned from the mother, of course).
Sorry that was a long response with a lot of information you did not necessarily ask for, but bonding rabbits is often a much more engineered task than many people realize. Knowing the spay/neuter status of all rabbits involved would be helpful.
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.