Yes this is an incest one, but considering how close father and son can look, I am not sure it is. Meaning I am not sure the uncle is really the brother of 'Nii-san'. Did we even learn his name? It seemed a bit strange that the brothers don't look remotely alike. And how easy it would be to clear up the confusion of "I love him, but not romanticly." Or "Our parents died when I was so young, that Nii-san is all I know of family." Or "I have a brother complex." which seems to be a thing that exists in manga a lot, never met anyone with a brother complex. Need to see more to see what comes out of this. There seems to be something deeper.
So far, kinda interesting. And the addition of the 3rd guy which seems to be only 'accepted' due to the fact that they worry about what the 3rd guy's father might do.
Katakoi Kazoku