looking at your pictures again and again.....and reading your post more carefully...... does the one in the picture of the threesome, on the left have a fluffy tail like the one in front?
If he has been ill, or is much younger, that could throw a person off., but I realized you had a close up of him while he was still in isolation.
I also got it through my fog that it came later and that the three are not an original group.
Look at it's behind, at the feathers and compare them to the pair. Since he is sickly and probably younger, we can't say if he is bigger or smaller without comparing him to his own siblings. Would you like to put a picture of bird #3 on, and take it when he is facing away from you. Throw some bread away from you if he won't turn around. Now, I'm thinking you have to cocks and a hen.
Marla Kaye