Only Baby Finch in the Cabbage Patch that Grew

My lady finch had four eggs in her clutch. One egg disappeared almost immediately, so I can only assume it got broken.  She sat on the remaining three a couple weeks before the first one hatched.  The other two never did hatch and they are still in there with the baby Finch that is really starting to look like a bird now that the feathers are growing in.  He/She is going to be white like the mother.  It is a mystery to me why the other two eggs did not hatch, but for her first nest, so far it is still a success in my book.  This baby is really loud and squeaks to be fed.