SmiYa0126
Free Ranging
Hi! Don't worry about having a lone chick, I had a lone chick and everything is ok 

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I know you are bummed and I'm really sorry it didn't make it. The 3rd photo shows it still had a lot of yolk to absorb, meaning even if you had assisted it probably would not have survived. Its often hard to know why a chick so far along in development dies in the shell. As an aside, the eggs are a beautiful color. How old is the hen that laid them? I will try to locate a very informative article I once read that addresses reasons a chick may die before hatch.
As far only one surviving chick, yes it would be better if there were more, but unless you have a local feed store carrying chicks this time of year, don't worry about it since there's nothing you can do.
The advantage of having a broody raise the chicks is that integration with the flock is much easier than if you are introducing new birds they don’t recognize. A good broody will protect her little and the chick will learn the ins and outs of the pecking order. It will be at the bottom once mama hen decides to wean the chick but from my experience, broody raised chicks are bothered far less than ones brought into the flock later on.
A chick that is raised all by itself gets lonely, and it can have trouble interacting with other chickens later, because it does not learn how when it is young.I do have concerns about having a lone chick now as I'm not convinced the last egg is alive.
Here is one article listing common reasons embros/chicks die before hatch. Many of the causes involve artificial incubation and may not apply to broody-incubated eggs. The fact your rooster is only 20 weeks old Might be a reason the chicks were too weak to fully develop and hatch, but to my knowledge it's usually eggs laid by older hens that have this problem.
https://extension.msstate.edu/content/trouble-shooting-failures-egg-incubation
A chick that is raised all by itself gets lonely, and it can have trouble interacting with other chickens later, because it does not learn how when it is young.
That applies to chicks brooded artifically, away from the flock. A chick raised by a hen is a very different case, and I do not think you have to worry about it.
A chick raised by a hen has mama for company (not lonely), and she teaches it how chickens interact. And when you put the hen & chick back with the flock, she helps the chick get properly integrated there too. So the chick will NOT have the social/interaction issues that would come from a chick being raised completely alone in a brooder.
Ah thank you. Our sweet girls stay on the eggs and took care of them and her chick for a few days but it looks like the other 3 chicks passed in their eggs hours before hatch unfortunately.After the first hatch, a day or two later the hen will leave the nest to care for the live chick/s and abandon any late bloomers so you'll need to make plans in that eventuality.