Why do roosters choose a hen of the same breed to mate with most of the time?

[Summerthegolden]

I have a Rooster and he is about 3 years old. When I was searching what breed he was I found something that said he was a Red Duck-wing German Bantam. I looked at more and saw it was not. So I started searching and found he was a Mille Fleur D'Uccle Bantam Rooster. When I first started he is the only rooster so far. When I started I had two Mille Fleur D'Uccle Bantam roosters and two Mille Fleur D'Uccle bantam hens the roosters chose a hen.
The rooster I still have is named Wraith, he still is with his hen he chose in the beginning. The other two died of natural causes. The hen that died was killed by a weasel. The other rooster was squished by a big 20 pound hay bale.

I also have a question do you think that it is not a good idea for the two living siblings to mate?

 

[oldhenlikesdogs]

Actually I don't think your question is correct as my roosters will mate with any breed, they do tend to only mate with those from the group they were brooded with, most of my older hens are never mated by the younger roosters.

As far as siblings mating it can be fine, but don't continue to cross the offspring without some genetic knowledge or you could end up with some deformities. Crossing siblings is a good way to set certain traits into a breeding line.