Faust and Doll when they reach full maturity.

Here's some fun facts about ShadowShifters:

Shadowshifter pregnancy lasts about a month, the babies developing at very fast rate to make it easier for the parents to protect their young.
The male birth is extremely violent, when it is time for the babies to be born, a red seam will show down the middle of the stomach, which the male will pry open to ‘birth’ the young. Their bodies pump out hormones and numbing chemicals to help keep them conscious through it, and one the babies are out, the stomach seals right back up.
The babies first meal is their ‘mother’s’ blood, to get the needed antibodies and first nourishment to insure survival.
Their minds grow much faster then their bodies, by the time they are eight, there minds are at the level of an eighteen year old, though they still will act like normal children.
At this point, they begin to seek out potential ‘mates’, those that they will add to their harem as they grow older, since shadowshifters do not have only one mate.
At seventeen/eighteen years, the young are able to breed, and in the case of twins, they will go into heat at the same time do to the extremely tight bonds developed.