Hi, welcome to the forum! I see the gender fairy has visited you.
FYI, the other girl is likely pregnant and the mom of this litter is possibly pregnant again. They can- and do- breed again very quickly after birthing.So do make sure they are on quality alfalfa pellets in addition to hay and keep an eye on their weights. Being pregnant while nursing can be very hard on a bun.
I wouldn't leave the girls together. Rabbits are territorial critters and are especially hormonal at the "teenage" stage they're likely in. They might be friendly today and fighting tomorrow. With the babies in the mix it's just not safe to leave the girls together. You can rebond them afterwards.
Are both girls the same color? If not, which color is the fur in the nest? Also, check for bare or thin spots of fur on the chest and over the nipples where the mom would have removed fur for the nest and to make nursing easier. I'm not sure how long it takes, but when the mom's milk lets down you will feel definite "breasts."
Do put the babies in a nest box. A shoe box that they can't crawl out of but that comfortably holds the mom is good. This will keep the babies from wriggling away and getting lost and cold. Put hay or wood shavings in the bottom, then scoop up the whole nest babies and all and gently place it in the box. While you're at it, check the babies over for any problems. Sometimes there will be a stillborn bun, the mom might not eat the placenta, or she overgrooms the babies andaccidentally harmed them.
If you can, now is a great time to get the boy neutered. It takes at least a month after the surgery for his sperm to die off and he can't be around the girls at all until then. So neuter now, and he'll be safe by the time the babies are weaned.
