Actually, there are four chicks, but they are very small and not really getting enough food to grow as fast as they should.
If they can just make it past the first ten days, they should be able to thermoregulate and will have a better chance. It is a very difficult task for Miep-VV. I don't think she would become aggressive with One Ring while they are both in the nest, with four very vulnerable chicks at risk.
One Ring, however, is well fed. One of the pics I have saved of him shows him with a large crop.