Hi and welcome to Binky Bunny!
Rabbits have been mix-sexed before, and people ended up with unexpected litters, so you have to be really certain that these are both females. Rabbits can reproduce at a very young age. Even if they are both females, at their age, they will need to be separated. They will very soon be entering puberty. The hormones that brings can mean attitude and aggression, which can lead to fighting. Rabbits can severely injure each other if they fight. Females can be spayed when they are around 6 months old. Find out from your vet when he or she prefers to do this. You will need to find a rabbit savvy vet for them. Then after their surgeries and a few weeks have passed for the hormones to level out, you can start the bonding process. Right now, they just have a temporary baby bunny bond.
Willow looks like a Dutch or a Dutch mix, since her fur pattern isn’t uniform. Luna does not look like a Rex. Her fur looks too long and she doesn’t have the short, curly whiskers that a Rex has. Rex fur is very short and velvety. They are both lovely bunnies.
There is a lot of good information on all the basics of rabbit care here. Click on the BUNNY INFO link at the top of the page.