How do your girls get on normally? Do they like each other? or are they always fighting?
If they like each other, there is a good chance that they will just concentrate on their own kittens whilst giving birth and help each other out when the kittens are born.
If they are bad tempered with each other then it would be a good idea to have a room for each queen to nest with her babies in peace, certainly to start off with. See how they fare and monitor their relationships to ensure that no sparks fly.
It is not generally thought to be a good idea for such young girls to have been allowed to become pregnant and for a queen to be just about a year old having had three litters is not very healthy for the poor girl. Nevertheless, there have been younger queens giving birth to babies - its not always the fault of the person who looks after them. Perhaps a queen only comes to a person when she is already pregnant and the person can only do their best for the cat.
Maybe after this you might like to consider having them spayed if you do not intend to breed from them. Certainly keep them indoors until they can be spayed if you wish to go this route. Hope everything goes well for you.
