That’s not a Rhode Island Red rooster. You can go to Feathersite and scroll down to get a photo of what a RIR looks like. I have not raised RIR so I had to look it up to make sure what the adult roosters looked like. That was my mistake not looking it up at first since I didn’t know for sure.
http://www.feathersite.com/Poultry/CGP/Reds/BRKRIR.html
How sure are you that those eggs came from that pair? Is it possible the eggs came from another pair of chickens?
That rooster looks like he has a Birchen gene, pretty close to a Black Copper Marans coloring. To get chicks like that he could not be pure for Birchen but that gene pair would be split with something else. Birchen can give black chicks but to get some yellow chicks like that, he could not be pure for Birchen. He’s have to be mixed with something else. He should be pure for the gold gene to have that red color since silver is dominant over gold, and the hen has silver.
If those chicks are from that rooster and hen, the yellow chicks will be male. Those did not get the Birchen gene from their father but got whatever else he had at that gene pair. If you had hatched any solid red chicks those would have been female but you didn’t hatch enough to get any of those.
The black chicks could be either male or female. They got the Birchen gene from their father and it is dominant over whatever that other gene at that gene pair is. When the feathers start to come in you should be able to sex then by feather color, but not in the down. The females will be pretty black with some red on their heads and the males will have some white feathering much like where their father has red. That’s the dominant silver from their mother dominating the gold from the father.
The only explanation I can come up with for that pair to have a black chick is that the rooster is not pure but is a mixed breed rooster. I has to be the rooster, not the hen.
. Here are pics of both
