I have a big age gap between my sons and I have a friend who has the same. I noticed that my younger son always modified his behaviour to get on with his brother and they got on just fine most of the time. My friend's younger son took a different approach. Rather than modify his behaviour to the socially acceptable norm, as his brother has told him to a million times (ie play the game correctly, don't shoot your own team mates, don't spoil the game for everyone, don't cry when you lose, don't impose what you want to do on everyone else, don't break my stuff ), the younger son has got everyone stirred up with tears and tantrums to the point where his Mum would tell the older brother off and blame him every time. This did, by the way, greatly improve when he hit 7.
In that instance it is the younger child who was being the manipulative one and you might want to consider if that is the case with yours. So easy for a little one to be annoying, turn on the waterworks and call for Mummy.
All of you shouting kick him out, have you got young adult children yourself? have you any idea how serious the housing crisis is? Have you got any idea how serious it is for a young adult to be homeless? How easy it is for things to spiral?
Issuing threats may work with your little kids . The consequences of issuing them to young adults is different. If you throw them out now, at their hour of need, while they are still getting established you can probably wave goodbye to your future relationship with them. And that would be a shame, all because a 6 year old couldn't play nicely.