2 brother cats 1 biting the other

[AhsataN]

I have two brother cats just over a year old both have been neutered. both have got on perfectly well ever since i got them as kittens.
they play fight with each other and are generally affectionate.
today one cat has been in all day and the other has been out. when bob returned harry sniffed him as usual then bite him behind his neck and held on until bob screamed out, he let go then grabbed him again and only let go when I pushed him off. he is placing one paw over his back like a male would with a female.
is this a dominance thing? I hope this isn't the start of them falling out or could just be hes been somewhere that smells strange?
anyone have any further knowledge? thanks

I have two neutered brothers as well, and one does bite the other's scruff and mount him. It may be a dominance thing, I'm not sure.

They get on just fine on the whole though :)

I have two neutered males (not brothers its true). They are 2 and 3yrs and one has started biting the other more noticably over the last 6-8mnths.

It begins as mutual grooming then turns into biting. It doesn't get too serious although I do tell them off to stop it. Some fur flies about and there's nipping and yelping. They also chase each other about the house, half in fun half seriously. I haven't noticed any injuries though so their bust ups can't be too bad.

But then again I often find them curled up asleep together.

I wonder if it's because they haven't been out as much. It's winter and cold and they spend most of the time inside atm. Even if I make them go out for a while they just sit and yowl at the door to come in again. They are quite spoilt and because I'm home most days they can do as they please which is to be in.