Sometimes a non-native speaker will go to inordinate lengths to avoid dealing with the dual number. It won’t work, though. There may be three children, but there are still only two parents.
Artistic license: If you have paid close attention to the backstory, you will realize that I fudged it a bit. By the time the non-dual child is big enough to be carried in the back of an amauti—she has to be able to hold her head up, which takes a couple of months—it would no longer be winter. There might still be snow on the ground (consider that the pivotal scene in Atanarjuat takes place in May or even June), but you definitely wouldn’t be building any snow houses.