
I was thinking along the lines of you being the resource he was guarding but usually other signs would be present as he would be watchful of you all the time and following you to make a cupa or go to the toilet etc but it doesn't sound like he is doing that. If he was I would suggest you get him used to not always being able to access you by closing the door behind you if you ni to the kitchen for a few min or putting him in his crate in the same room as you for short times to stop this.
Will he stop barking if asked to - ie if he can see you near the door? again its a presence question.
Without seeing him and how he interacts with both you and the other dogs it's hard to tell.
Will he lie quietly if you put him out with a stuffed kong or other distractor?
Hopefully some others will offer advice soon - I am heading off to Crufts later today so won't be online much.
I may not have been much help